Plastic lens compositions

ABSTRACT

An apparatus for preparing a plastic eyeglass lens includes a coating unit and a lens curing unit. The apparatus is preferably configured to allow the operation of both the coating unit and the lens curing unit. The apparatus may also include a post-cure unit and a controller. The controller is configured to control the operation of the coating unit, the lens curing unit and the post-cure unit. The lens forming unit may include an LCD filter disposed between activating light sources and a mold assembly. The mold assembly preferably includes two mold members held together by a gasket. The gasket preferably includes four protrusions spaced at 90 degree intervals about the gasket. A lens forming composition may include a first photochromic compound, a second photochromic compound and a light effector. The light effector may alter the color of a lens when exposed to photochromic activating light, when compared to a lens formed from a lens forming composition which does not include a light effector.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to eyeglass lenses. Moreparticularly, the invention relates to a lens forming composition,system and method for making photochromic, ultraviolet/visible lightabsorbing, and colored plastic lenses by curing the lens formingcomposition using activating light.

2. Description of the Relevant Art

It is conventional in the art to produce optical lenses by thermalcuring techniques from the polymer of diethylene glycolbis(allyl)-carbonate (DEG-BAC). In addition, optical lenses may also bemade using ultraviolet (“UV”) light curing techniques. See, for example,U.S. Pat. No. 4,728,469 to Lipscomb et al., U.S. Pat. No. 4,879,318 toLipscomb et al., U.S. Pat. No. 5,364,256 to Lipscomb et al., U.S. Pat.No. 5,415,816 to Buazza et al., U.S. Pat. No. 5,529,728 to Buazza etal., U.S. Pat. No. 5,514,214 to Joel et al., U.S. Pat. No. 5,516,468 toLipscomb, et al., U.S. Pat. No. 5,529,728 to Buazza et al., U.S. Pat.No. 5,689,324 to Lossman et al., and U.S. patent application Ser. No.07/425,371 filed Oct. 26, 1989, Ser. No. 08/439,691 filed May 12, 1995,Ser. No. 08/454,523 filed May 30, 1995, Ser. No. 08/453,770 filed May30, 1995, Ser. No. 08/636,510 filed Apr. 19, 1996, Ser. No. 08/663,703filed Jun. 14, 1996, Ser. No. 08/666,062 filed Jun. 14, 1996, Ser. No.08/853,134 filed May 8, 1997, Ser. No. 08/844,557 filed Apr. 18, 1997,Ser. No. 08/904,289 filed Jul. 31, 1997, and Ser. No. 08/959,973 filedOct. 29, 1997, all of which are hereby specifically incorporated byreference.

Curing of a lens by ultraviolet light tends to present certain problemsthat must be overcome to produce a viable lens. Such problems includeyellowing of the lens, cracking of the lens or mold, optical distortionsin the lens, and premature release of the lens from the mold. Inaddition, many of the useful ultraviolet light-curable lens formingcompositions exhibit certain characteristics that increase thedifficulty of a lens curing process. For example, due to the relativelyrapid nature of ultraviolet light initiated reactions, it is a challengeto provide a composition that is ultraviolet light curable to form aneyeglass lens. Excessive exothermic heat tends to cause defects in thecured lens. To avoid such defects, the level of photoinitiator may bereduced to levels below what is customarily employed in the ultravioletcuring art.

While reducing the level of photoinitiator addresses some problems, itmay also cause others. For instance, lowered levels of photoinitiatormay cause the material in regions near an edge of the lens and proximatea gasket wall in a mold cavity to incompletely cure due to the presenceof oxygen in these regions (oxygen is believed to inhibit curing of manylens forming compositions or materials). Uncured lens formingcomposition tends to result in lenses with “wet” edges covered by stickyuncured lens forming composition. Furthermore, uncured lens formingcomposition may migrate to and contaminate the optical surfaces of thelens upon demolding. The contaminated lens is then often unusable.

Uncured lens forming composition has been addressed by a variety ofmethods (see, e.g., the methods described in U.S. Pat. No. 5,529,728 toBuazza et al). Such methods may include removing the gasket and applyingeither an oxygen barrier or a photoinitiator enriched liquid to theexposed edge of the lens, and then re-irradiating the lens with a dosageof ultraviolet light sufficient to completely dry the edge of the lensprior to demolding. During such irradiation, however, higher thandesirable levels of irradiation, or longer than desirable periods ofirradiation, may be required. The additional ultraviolet irradiation mayin some circumstances cause defects such as yellowing in the lens.

The low photoinitiator levels utilized in many ultraviolet curable lensforming compositions may produce a lens that, while fully-cured asmeasured by percentage of remaining double bonds, may not possesssufficient cross-link density on the lens surface to provide desirabledye absorption characteristics during the tinting process.

Various methods of increasing the surface density of such ultravioletlight curable lenses are described in U.S. Pat. No. 5,529,728 to Buazzaet al. In one method, the lens is de-molded and then the surfaces of thelens are exposed directly to ultraviolet light. The relatively shortwavelengths (around 254 nm) provided by some ultraviolet light sources(e.g., a mercury vapor lamp) tend to cause the material to cross-linkquite rapidly. An undesirable effect of this method, however, is thatthe lens tends to yellow as a result of such exposure. Further, anycontaminants on the surface of the lens that are exposed to shortwavelengths of high intensity ultraviolet light may cause tint defects.

Another method involves exposing the lens to relatively high intensityultraviolet radiation while it is still within a mold cavity formedbetween glass molds. The glass molds tend to absorb the more effectiveshort wavelengths, while transmitting wavelengths of about 365 nm. Thismethod generally requires long exposure times and often the infraredradiation absorbed by the lens mold assembly will cause prematurerelease of the lens from a mold member. The lens mold assembly may beheated prior to exposure to high intensity ultraviolet light, therebyreducing the amount of radiation necessary to attain a desired level ofcross-link density. This method, however, is also associated with ahigher rate of premature release.

It is well known in the art that a lens mold/gasket assembly may beheated to cure the lens forming composition from a liquid monomer to asolid polymer. It is also well known that such a lens may be thermallypostcured by applying convective heat to the lens after the molds andgaskets have been removed from the lens.

In this application the terms “lens forming material” and “lens formingcompositions” are used interchangeably.

SUMMARY OF THE INVENTION

An embodiment of an apparatus for preparing an eyeglass lens isdescribed. The apparatus includes a coating unit and a lens curing unit.The coating unit may be configured to coat either mold members orlenses. Preferably, the coating unit is a spin coating unit. The lenscuring unit may be configured to direct activating light toward moldmembers. The mold members are part of a mold assembly that may be placedwithin the lens curing unit. Depending on the type of lens formingcomposition used, the apparatus may be used to form photochromic andnon-photochromic lenses. The apparatus is preferably configured to allowthe operation of both the coating unit and the lens curing unitsubstantially simultaneously.

The coating unit is preferably a spin coating unit. The spin coatingunit preferably comprises a holder for holding an eyeglass lens or amold member. The holder is preferably coupled to a motor that ispreferably configured to rotate the holder. An activating light sourcemay be incorporated into a cover. The cover may be drawn over the bodyof the lens curing unit, covering the coating units. The activatinglight source is preferably positioned, when the cover is closed, suchthat activating light may be applied to the mold member or lenspositioned within the coating unit. An activating light source may be anultraviolet light source, an actinic light source (e.g., a light sourceproducing light having a wavelength between about 380 nm to 490 nm), avisible light source and/or an infra-red light source. Preferably, theactivating light source is an ultraviolet light source.

The lens curing unit includes at least one, preferably two activatinglight sources for irradiating a mold assembly. Mold assembly holders maybe positionable within the lens forming apparatus such that theactivating light may be applied to the mold member during use. A filteris preferably positioned between the mold assemblies and the activatinglight source. The filter is preferably configured to manipulate theintensity of activating light that is directed toward the mold members.The filter may be a hazy filter that includes a frosted glass member.Alternatively, the filter may be a liquid crystal display (“LCD”) panel.

An LCD panel for use as a filter is preferably a monochrometrans-flective panel with the back light and reflector removed. Theintensity of the light is preferably reduced as the light passes throughthe LCD panel. The LCD panel is preferably programmable such that thelight transmissibility of the LCD panel may be altered. In use, apredetermined pattern of light and dark regions may be displayed on theLCD panel to alter the intensity of light passing through the panel. Oneadvantage of an LCD panel filter is that a pattern may be altered duringa curing cycle. For example, the pattern of light and dark regions maybe manipulated such that a lens is initially cured from the center ofthe lens, then the curing may be gradually expanded to the outer edgesof the lens. This type of curing pattern may allow a more uniformlycured lens to be formed.

Another advantage is that the LCD panel may be used as a partial shutterto reduce the intensity of light reaching the mold assembly. Byblackening the entire LCD panel the amount of light reaching any portionof the mold assembly may be reduced. In this manner, the LCD may be usedto create “pulses” of light by alternating between a transmissive anddarkened mode.

In another embodiment, an LCD panel may be used to allow differentpatterns and/or intensities of light to reach two separate moldassemblies. If the mold assemblies are being used to create lenseshaving significantly different powers, each mold assembly may require asignificantly different light irradiation pattern and/or intensity. Theuse of an LCD filter may allow the irradiation of each of the moldassemblies to be controlled individually.

When non-LCD type filters are used, it may be necessary to maintain alibrary of filters for use in the production of different types ofprescription lenses. Typically, each individual prescription will need aparticular filter pattern to obtain a high quality lens. Since an LCDpanel is programmable in a variety of patterns, it is believed that onemay use a single LCD panel, rather than a library of filters. The LCDpanel may be programmed to fit the needs of the specific type of lensbeing formed.

The LCD panel filters may be coupled to a programmable logic device thatmay be used to design and store patterns for use during curing. FIG.7-10 show a number of patterns that may be generated on an LCD panel andused to filter activating light. Each of these patterns is preferablyused for the production of a lens having a specific prescription power.

The lens forming apparatus may include a post-cure unit. The post-cureunit is preferably configured to apply heat and activating light to moldassemblies or lenses disposed within the post-cure unit.

The lens forming apparatus may also include a programmable controllerconfigured to substantially simultaneously control the operation of thecoating unit, the lens curing unit and the post-cure unit. The apparatusmay include a number of light probes and temperature probes disposedwithin the coating unit, lens curing unit, and the post-cure unit. Theseprobes preferably relay information about the operation of theindividual units to the controller. The information relayed may be usedto control the operation of the individual units. The operation of eachof the units may also be controlled based on the prescription of thelens being formed.

The controller may be configured to control various operations of thecoating unit. For example, when a spin coating unit is used thecontroller may control the rotation of the lens or mold member during acoating process (e.g., whether the lens or mold members are rotated ornot and/or the speed of rotation) and the operation of the coating unitlamps (e.g., whether the lamps are on or off and/or the time the lampsare on).

The controller may also be configured to control the various operationsof the lens curing unit. Some of the operations that may be controlledor measured by the controller include: (i) measuring the ambient roomtemperature; (ii) determining the dose of light (or initial dose oflight in pulsed curing applications) required to cure the lens formingcomposition, based on the ambient room temperature; (iii) applying theactivating light with an intensity and duration sufficient to equal thedetermined dose; (iv) measuring the composition's temperature responseduring and subsequent to the application of the dose of light; (v)calculating the dose required for the next application of activatinglight (in pulsed curing applications); (vi) applying the activatinglight with an intensity and duration sufficient to equal the determinedsecond dose; (vii) determining when the curing process is complete bymonitoring the temperature response of the lens forming compositionduring the application of activating light; (viii) turning the upper andlower light sources on and off independently; (ix) monitoring the lamptemperature, and controlling the temperature of the lamps by activatingcooling fans proximate the lamps; and (x) turning the fans on/off orcontrolling the flow rate of an air stream produced by a fan to controlthe composition temperature;

The controller may also be configured to control the operation of thepost-cure unit. Some of the operations that may be controlled includecontrol of the operation of the lamps (e.g., whether the lamps are on oroff and the time the lamps are on); and operation of the heating device(e.g., whether the heating unit is turned on or off and/or the amount ofheat produced by the heating device).

Additionally, the controller provides system diagnostics and informationto the operator of the apparatus. The controller may notify the userwhen routine maintenance is due or when a system error is detected. Thecontroller may also manage an interlock system for safety and energyconservation purposes. The controller may prevent the lamps fromoperating when the operator may be exposed to light from the lamps.

The controller may also be configured to interact with the operator. Thecontroller preferably includes an input device and a display screen. Anumber of operations controlled by the controller, as described above,may be dependent on the input of the operator. The controller mayprepare a sequence of instructions based on the type of lens (clear,ultraviolet/visible light absorbing, photochromic, colored, etc.),prescription, and type of coatings (e.g., scratch resistant, adhesionpromoting, or tint) inputted by an operator.

A variety of lens forming compositions may be cured to form a plasticeyeglass lens in the above described apparatus. Colored lenses,photochromic lenses, and ultraviolet/visible light absorbing colorlesslenses may be formed. The lens forming compositions may be formulatedsuch that the conditions for forming the lens (e.g., curing conditionsand post cure conditions) may be similar without regard to the lensbeing formed. In an embodiment, a clear lens may be formed under similarconditions used to form photochromic lenses by adding a colorless,non-photochromic ultraviolet/visible light absorbing compound to thelens forming composition. The curing process for forming a photochromiclens is such that higher doses of activating light than are typicallyused for the formation of a clear, non-ultraviolet/visible lightabsorbing lens may be required. In an embodiment, ultraviolet/visiblelight absorbing compounds may be added to a lens forming composition toproduce a substantially clear lens under the more intense dosingrequirements used to form photochromic lenses. The ultraviolet/visiblelight absorbing compounds may take the place of the photochromiccompounds, making curing at higher doses possible for clear lenses. Anadvantage of adding the ultraviolet/visible light absorbers to the lensforming composition is that the clear lens formed may offer betterprotection against ultraviolet/visible light rays than a clear lensformed without such compounds.

An embodiment relates to an improved gasket for engaging a mold. Thegasket is preferably configured to engage a first mold set for forming afirst lens of a first power. The gasket preferably includes at leastfour discrete projections for spacing mold members of a mold set. Theprojections are preferably arranged on an interior surface of thegasket. The projections are preferably evenly spaced around the interiorsurface of the gasket; in a preferred embodiment, the spacing betweeneach projection is about 90 degrees.

In another embodiment, an improved gasket includes a fill port forreceiving a lens forming composition while fully engaged to a mold set.The fill port preferably extends from an interior surface of the gasketto an exterior surface of the gasket. Consequently, the gasket need notbe partially disengaged from a mold member of a mold set in order toreceive a lens forming composition.

In another embodiment, a mold/gasket assembly for making plasticprescription lenses preferably includes a first mold set for forming afirst lens of a first power and a gasket for engaging the first moldset. The first mold set may contain a front mold member and a back moldmember. The back mold member is also known as the convex mold member.The back mold member preferably defines the concave surface of a convexlens. The gasket is preferably characterized by at least four discreteprojections for spacing the front mold member from the back mold member.A mold cavity for retaining a lens forming composition is preferably atleast partially defined by the front mold member, the back mold member,and the gasket. The back mold member preferably has a steep axis and aflat axis. Each of the projections preferably forms an oblique anglewith the steep and the flat axis of the mold members. In a preferredembodiment, these angles may each be about 45 degrees. Since the gasketdoes not include a continuous lip along its interior surface for spacingmold members, as is conventional in the art, the gasket may beconfigured to engage a large variety of mold sets. For example, thegasket may be configured to engage a second mold set for forming asecond lens of a second power.

In another embodiment, a mold/gasket assembly for making plasticprescription lenses includes a mold set for forming a lens and a gasketconfigured to engage the mold set. The gasket is preferablycharacterized by a fill port for receiving a lens forming compositionwhile the gasket is fully engaged to the mold. The fill port preferablyextends from an interior surface to an exterior surface of the gasket.The mold set preferably contains at least a front mold member and a backmold member. A mold cavity for retaining a lens forming composition ispreferably at least partially defined by the front mold member, the backmold member, and the gasket.

A method for making a plastic eyeglass lens is described. The methodpreferably includes engaging a gasket with a first mold set for forminga first lens of a first power. The first mold set preferably contains atleast a front mold member and a back mold member. A mold cavity forretaining a lens forming composition may be at least partially definedby the front mold member, the back mold member, and the gasket. Thegasket is preferably characterized by at least four discrete projectionsarranged on an interior surface thereof for spacing the front and backmold members. Engaging the gasket with the mold set preferably includespositioning the back mold members such that each of the projectionsforms an oblique angle with the steep and flat axis of the back moldmember. In a preferred embodiment, this angle is about 45 degrees. Themethod preferably further includes introducing a lens formingcomposition into the mold cavity and curing the lens formingcomposition.

An additional embodiment provides a method for making a plastic eyeglasslens. The method preferably includes engaging a gasket with a first moldset for forming a first lens of a first power. The first mold setpreferably contains at least a front mold member and a back mold member.A mold cavity for retaining a lens forming composition may be at leastpartially defined by the front mold member, the back mold member, andthe gasket. Preferably, the method further includes introducing a lensforming composition through a fill port, wherein the front and back moldmembers remain fully engaged with the gasket during the introduction ofthe lens forming composition. The lens forming composition may then becured.

In an embodiment, a composition that includes two or more photochromiccompounds may further include a light effector composition to produce alens that exhibits an activated color that differs from an activatedcolor produced by the photochromic compounds without the light effectorcomposition. The activated color is defined as the color a lens achieveswhen exposed to a photochromic activating light source (e.g., sunlight).A photochromic activating light source is defined as any light sourcethat produces light having a wavelength that causes a photochromiccompound to become colored. Photochromic activating light is defined aslight that has a wavelength capable of causing a photochromic compoundto become colored. The photochromic activating wavelength band isdefined as the region of light that has a wavelength that causescoloring of photochromic compounds. The light effector composition mayinclude any compound that exhibits absorbance of at least a portion ofthe photochromic activating wavelength band. Light effector compositionsmay include photoinitiators, ultraviolet/visible light absorbers,ultraviolet light stabilizers, and dyes. In this manner, the activatedcolor of a lens may be altered without altering the ratio and orcomposition of the photochromic compounds. By using a light effectorcomposition, a single lens forming composition may be used as a basesolution to which a light effector may be added in order to alter theactivated color of the formed lens.

The addition of a light effector composition that absorbs photochromicactivating light may cause a change in the activated color of the formedlens. The change in activated color may be dependent on the range ofphotochromic activating light absorbed by the light effectorcomposition. The use of different light effector compositions may allowan operator to produce photochromic lenses with a wide variety ofactivated colors (e.g., red, orange, yellow, green, blue, indigo,violet, gray, or brown).

In an embodiment, an ophthalmic eyeglass lens may be made from anactivating light curable lens forming composition comprising a monomercomposition and a photoinitiator composition. The monomer compositionpreferably includes a polyethylenic functional monomer. Preferably, thepolyethylenic functional monomer composition includes an aromaticcontaining polyether polyethylenic functional monomer. In oneembodiment, the polyethylenic functional monomer is preferably anethoxylated bisphenol A di(meth)acrylate.

The monomer composition may include additional monomers to modify theproperties of the formed eyeglass lens and/or the lens formingcomposition. Monomers which may be used in the monomer compositioninclude polyethylenic functional monomers containing groups selectedfrom acrylyl or methacrylyl.

In one embodiment, the photoinitiator composition preferably includesbis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)phosphine oxide,commercially available from Ciba Additives in Tarrytown, N.Y. under thetrade name of Irgacure 819. In another embodiment, the photoinitiatorcomposition may include a mixture of photoinitiators. Preferably, amixture of Irgacure 819 and 1-hydroxycyclohexylphenyl ketone,commercially available from Ciba Additives under the trade name ofIrgacure 184, is used.

In another embodiment, an ophthalmic eyeglass lens may be made from anactivating light curable lens forming composition comprising a monomercomposition, a photoinitiator composition and a co-initiatorcomposition. An activating light absorbing compound may also be present.An activating light absorbing compound is herein defined as a compoundwhich absorbs at least a portion of the activating light. The monomercomposition preferably includes a polyethylenic functional monomer.Preferably, the polyethylenic functional monomer is an aromaticcontaining polyether polyethylenic functional monomer. In oneembodiment, the polyethylenic functional monomer is preferably anethoxylated bisphenol A di(meth)acrylate.

The co-initiator composition preferably includes amine co-initiators.Preferably, acrylyl amines are included in the co-initiator composition.In one embodiment, the co-initiator composition preferably includes amixture of CN-384 and CN-386.

Examples of activating light absorbing compounds includes photochromiccompounds, UV stabilizers, UV absorbers, and/or dyes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description as well as further objects, features andadvantages of the methods and apparatus of the present invention will bemore fully appreciated by reference to the following detaileddescription of presently preferred but nonetheless illustrativeembodiments in accordance with the present invention when taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a perspective view of a plastic lens forming apparatus.

FIG. 2 depicts a perspective view of a spin coating unit.

FIG. 3 depicts a cut-away side view of a spin coating unit.

FIG. 4 depicts a perspective view of a plastic lens forming apparatuswith a portion of the body removed.

FIG. 5 depicts a perspective view of the components of a lens curingunit.

FIG. 6 depicts a perspective view of a plastic lens forming apparatuswith a portion of the body removed and the coating units removed.

FIG. 7-10 depict various LCD filter patterns.

FIG. 11 depicts a mold assembly.

FIG. 12 depicts a post-cure unit.

FIG. 13 depicts a view of an embodiment of a heat source and a heatdistributor.

FIG. 14 depicts a view of various embodiments of a heat source and heatdistributors.

FIG. 15 depicts a view of an embodiment of a heat source and a heatdistributor.

FIG. 16 depicts a view of an embodiment of two mold members and agasket.

FIG. 17 depicts a plot of the temperature of the lens formingcomposition versus time during the application of activating lightpulses.

FIG. 18 depicts a schematic diagram of a lens curing apparatus with alight sensor and controller.

FIG. 19 depicts a view of an embodiment of a system simultaneouslyemploying both a flash light source and a continuous activating (e.g.,fluorescent) light source.

FIG. 20 depicts an embodiment of a system simultaneously employing twoflash light sources.

FIG. 21 depicts an embodiment of a system employing an activating lightcontroller.

FIG. 22 depicts a graph illustrating a temperature profile of acontinuous radiation cycle.

FIG. 23 depicts a graph illustrating temperature profiles for acontinuous irradiation cycle and a pulse irradiation cycle employed witha mold/gasket set having a 3.00D base curve, and while applying cooledair at 58° F. to the mold/gasket set.

FIG. 24 depicts a chart illustrating qualitative relationships amongcuring cycle variables.

FIG. 25 depicts a graph illustrating temperature profiles for one curingcycle for a mold/gasket set having a 6.00D base curve and used withthree different light levels.

FIG. 26 depicts a graph illustrating continuous and pulsed temperatureprofiles for a curing cycle employing a mold/gasket set with a 6.00Dbase curve.

FIG. 27 depicts a graph illustrating continuous and pulsed temperatureprofiles for a curing cycle employing a mold/gasket set with a 4.50Dbase curve.

FIG. 28 depicts a graph illustrating continuous and pulsed temperatureprofiles for a curing cycle employing a mold/gasket set with a 3.00Dbase curve.

FIG. 29 depicts a cross sectional view of a flat-top bifocal mold.

FIG. 30 depicts a plot of % transmittance of light versus wavelength fora photochromic lens.

FIG. 31 depicts a plot of % transmittance of light versus wavelength forboth a colorless lens containing ultraviolet/visible light absorbers anda lens containing no ultraviolet/visible light absorbers.

FIG. 32 depicts an isometric view of an embodiment of a gasket.

FIG. 33 depicts a top view of the gasket of FIG. 1.

FIG. 34 depicts a cross-sectional view of an embodiment of a mold/gasketassembly.

FIG. 35 depicts an isometric view of an embodiment of a gasket.

FIG. 36 depicts a top view of the gasket of FIG. 4.

FIG. 37 depicts a graph showing the absorption ranges of a variety ofphotochromic compounds and light effectors.

FIG. 38 depicts a plastic lens forming apparatus which includes two lenscuring units.

FIG. 39 depicts chemical structure of acrylated amines.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Apparatus, operating procedures, equipment, systems, methods, andcompositions for lens curing using activating light are available fromRapid Cast, Inc., Q2100, Inc., and Fast Cast, Inc. in Louisville, Ky.

Referring now to FIG. 1, a plastic lens curing apparatus is generallyindicated by reference numeral 10. As shown in FIG. 1, lens formingapparatus 10 includes at least one coating unit 20, a lens curing unit30, a post-cure unit 40, and a controller 50. Preferably, apparatus 10includes two coating units 20. Coating unit 20 is preferably configuredto apply a coating layer to a mold member or a lens. Preferably, coatingunit 20 is a spin coating unit. Lens curing unit 30 includes anactivating light source for producing activating light. As used herein“activating light” means light that may affect a chemical change.Activating light may include ultraviolet light (e.g., light having awavelength between about 300 nm to about 400 nm), actinic light, visiblelight or infrared light. Generally, any wavelength of light capable ofaffecting a chemical change may be classified as activating. Chemicalchanges may be manifested in a number of forms. A chemical change mayinclude, but is not limited to, any chemical reaction that causes apolymerization to take place. Preferably the chemical change causes theformation of an initiator species within the lens forming composition,the initiator species being capable of initiating a chemicalpolymerization reaction. The activating light source is preferablyconfigured to direct light toward a mold assembly. Post-cure unit 40 ispreferably configured to complete the polymerization of plastic lenses.Post-cure unit 40 preferably includes an activating light source and aheat source. Controller 50 is preferably a programmable logiccontroller. Controller 50 is preferably coupled to coating units 20,lens curing unit 30, and post-cure unit 40, such that the controller iscapable of substantially simultaneously operating the three units 20,30, and 40. Controller 50 may be a computer.

A coating unit for applying a coating composition to a lens or a moldmember and then curing the coating composition is described in U.S. Pat.Nos. 4,895,102 to Kachel et al., 3,494,326 to Upton, and 5,514,214 toJoel et al. (all of which are incorporated herein by reference). Inaddition, the apparatus shown in FIGS. 2 and 3 may also be used to applycoatings to lenses or mold members.

FIG. 2 depicts a pair of spin coating units 102 and 104. These spincoating units may be used to apply a scratch resistant coating or a tintcoating to a lens or mold member. Each of the coating units includes anopening through which an operator may apply lenses and lens moldassemblies to a holder 108. Holder 108 is preferably partiallysurrounded by barrier 114. Barrier 114 is preferably coupled to a dish115. As shown in FIG. 3, the dish edges may be inclined to form aperipheral sidewall 121 that merges with barrier 114. The bottom 117 ofthe dish is preferably substantially flat. The flat bottom preferablyhas a circular opening that allows an elongated member 109 coupled tolens holder 108 to extend through the dish 115.

Holder 108 is preferably coupled to a motor 112 via elongated member109. Motor 112 is preferably configured to cause rotation of holder 108.In such a case, motor 112 is preferably configured to cause rotation ofelongated member 109, that in turn causes the rotation of holder 108.The coating unit 102/104, may also include an electronic controller 140.Electronic controller 140 is preferably coupled to motor 112 to controlthe rate at which holder 108 is rotated by motor 112. Electroniccontroller 140 may be coupled to a programmable logic controller, suchas controller 50, shown in FIG. 1. The programmable logic controller maysend signals to the electronic controller to control the rotationalspeed of holder 108. Preferably, motor 112 is configured to rotateholder 108 at different rates. Motor 112 is preferably capable ofrotating the lens or mold member at a rate of up to 1500 revolutions perminute (“RPM”).

In one embodiment, barrier 114 has an interior surface that may be madeor lined with an absorbent material such as foam rubber. Preferably,this absorbent material is disposable and removable. The absorbentmaterial absorbs any liquids that fall off a lens or mold member duringuse. Alternatively, the interior surface of barrier 114 may besubstantially non-absorbent, allowing any liquids used during thecoating process to move down barrier 114 into dish 115.

Coating units 20, are preferably positioned in a top portion 12 of lensforming apparatus 10, as depicted in FIG. 1. A cover 22 is preferablycoupled to body 14 of the lens forming apparatus to allow top portion 12to be covered during use. A light source 23 is preferably positioned onan inner surface of cover 22. The light source includes at least onelamp 24, preferably two or more lamps, positioned on the inner surfaceof cover 22. Lamps 24 may be positioned such that the lamps are orientedabove the coating units 20 when cover 22 is closed. Lamps 24 preferablyemit activating light upon the lenses or mold members positioned withincoating units 20. Lamps may have a variety of shapes including, but notlimited to, linear (as depicted in FIG. 1), square, rectangular,circular, or oval. Activating light sources preferably emit light havinga wavelength that will initiate curing of various coating materials. Forexample, most currently used coating materials are preferably curable byactivating light having wavelengths in the ultraviolet region, thereforethe light sources should exhibit strong ultraviolet light emission. Thelight sources should, preferably, produce minimal heat during use. Thus,lamps 24 will preferably have low heat output. Lamps that exhibit strongultraviolet light emission have a peak output at a wavelength in theultraviolet light region, between about 200 nm to about 400 nm,preferably the peak output is between about 200 nm to 300 nm, and morepreferably at about 254 nm. In one embodiment, lamps 24 may be lampsthat have a peak output in the ultraviolet light region, and haverelatively low heat output. Such lights are commonly known as“germicidal” lights and any such light may be used. A “germicidal” lightemitting light with a peak output in the desired ultraviolet region iscommercially available from Voltarc, Inc. of Fairfield, Conn. as modelUV-WX G10T5.

An advantage of using a spin coating unit is that lamps of a variety ofshapes may be used (e.g., linear lamps) for the curing of the coatingmaterials. In one embodiment, a coating material is preferably cured ina substantially uniform manner to ensure that the coating is formeduniformly on the mold member or lens. With a spin coating unit, theobject to be coated may be spun at speeds high enough to ensure that asubstantially uniform distribution of light reaches the object duringthe curing process, regardless of the shape of the light source. The useof a spin coating unit preferably allows the use of commerciallyavailable linear light sources for the curing of coating materials.

A switch may be incorporated into cover 22. The switch is preferablyelectrically coupled to light source 23 such that the switch must beactivated prior to turning the light source on. Preferably, the switchis positioned such that closing the cover causes the switch to becomeactivated. In this manner, the lights will preferably remain off untilthe cover is closed, thus preventing inadvertent exposure of an operatorto the light from light source 23.

During use a lens or lens mold assembly may be placed on the lens holder108. The lens holder 108 may include a suction cup connected to a metalbar. The concave surface of the suction cup may be attachable to a faceof a mold or lens, and the convex surface of the suction cup may beattached to a metal bar. The metal bar may be coupled to motor 112. Thelens holder may also include movable arms and a spring assembly that maybe together operable to hold a lens against the lens holder with springtension during use.

As shown in FIG. 4, the curing unit 30 may include an upper light source214, a lens drawer assembly 216, and a lower light source 218. Lensdrawer assembly 216 preferably includes a mold assembly holder 220, morepreferably at least two mold assembly holders 220. Each of the moldassembly holders 220 is preferably configured to hold a pair of moldmembers that together with a gasket form a mold assembly. The lensdrawer assembly 216 is preferably slidingly mounted on a guide. Duringuse, mold assemblies may be placed in the mold assembly holders 220while the lens drawer assembly is in the open position (i.e., when thedoor extends from the front of the lens curing unit). After the moldassemblies have been loaded into the mold holder 220 the door may beslid into a closed position, with the mold assemblies directly under theupper light source 214 and above the lower light source 218. Vents (notshown) may be placed in communication with the lens curing unit to allowa stream of air to be directed toward the mold members when the moldmembers are positioned beneath the upper lamps. An exhaust fan (notshown) may communicate with the vents to improve the circulation of airflowing through the lens curing unit.

As shown in FIGS. 4 and 5, it is preferred that the upper light source214 and lower light source 216 include a plurality of activating lightgenerating devices or lamps 240. Preferably, the lamps are orientedproximate each other to form a row of lights, as depicted in FIG. 4.Preferably, three or four lamps are positioned to provide substantiallyuniform radiation over the entire surface of the mold assembly to becured. The lamps 240, preferably generate activating light. Lamps 240may be supported by and electrically connected to suitable fixtures 242.Lamps 240 may generate either ultraviolet light, actinic light, visiblelight, and/or infrared light. The choice of lamps is preferably based onthe monomers used in the lens forming composition. In one embodiment,the activating light may be generated from a fluorescent lamp. Thefluorescent lamp preferably has a strong emission spectra in the 380 to490 nm region. A fluorescent lamp emitting activating light with thedescribed wavelengths is commercially available from Philips as modelTLD-15W/03. In another embodiment, the lamps may be ultraviolet lights.

In one embodiment, the activating light sources may be turned on and offquickly between exposures. Flasher ballasts 250, depicted in FIG. 6, maybe used for this function. The flasher ballast may be positioned beneaththe coating unit. A flasher ballast 250 may operate in a standby modewherein a low current is supplied to the lamp filaments to keep thefilaments warm and thereby reduce the strike time of the lamp. Such aballast is commercially available from Magnatek, Inc of Bridgeport,Conn. Power supply 252 may also be located proximate the flasherballasts, underneath the coating unit.

FIG. 18 schematically depicts a light control system. The light sources214 in lens curing unit 30 apply light towards the mold assembly 352. Alight sensor 700 may be located adjacent the light sources 214.Preferably, the light sensor 700 is a photoresistor light sensor(photodiodes or other light sensors may also be usable in thisapplication). The light sensor 700 with a filter 750 may be connected tolamp driver 702 via wires 704. Lamp driver 702 sends a current throughthe light sensor 700 and receives a return signal from the light sensor700. The return signal may be compared against an adjustable set point,and then the electrical frequency sent to the light sources 214 viawires 706 may be varied depending on the differences between the setpoint and the signal received from the light sensor 700. Preferably, thelight output is maintained within about +/−1.0 percent.

One “lamp driver” or light controller is a Mercron Model FX0696-4 andModel FX06120-6 (Mercron, Inc., Dallas, Tex., U.S.A.). These lightcontrollers are described in U.S. Pat. Nos. 4,717,863 and 4,937,470.

In an embodiment, a flash lamp emits activating light pulses to cure thelens forming material. It is believed that a flash lamp would provide asmaller, cooler, less expensive, and more reliable light source thanother sources. The power supply for a flash lamp tends to drawrelatively minimal current while charging its capacitor bank. The flashlamp discharges the stored energy on a microsecond scale to produce veryhigh peak intensities from the flash tube itself Thus flash lamps tendto require less power for operation and generate less heat than otherlight sources used for activating light curing. A flash lamp may also beused to cure a lens coating.

In an embodiment, the flash lamp used to direct activating light towardat least one of the mold members is a xenon light source. The lenscoating may also be cured using a xenon light source. Referring to FIG.21, xenon light source 980 preferably contains photostrobe 992 having atube 996 and electrodes to allow the transmission of activating light.The tube may include borosilicate glass or quartz. A quartz tube willgenerally withstand about 3 to 10 times more power than a hard glasstube. The tube may be in the shape of a ring, U, helix, or it may belinear. The tube may include capacitive trigger electrode 995. Thecapacitive trigger electrode may include a wire, silver strip, orconductive coating located on the exterior of tube 996. The xenon lightsource is preferably adapted to deliver pulses of light for a durationof less than about 1 second, more preferably between about {fraction(1/10)} of a second and about {fraction (1/1000)} of a second, and morepreferably still between about {fraction (1/400)} of a second and{fraction (1/600)} of a second. The xenon source may be adapted todeliver light pulses about every 4 seconds or less. The relatively highintensity of the xenon lamp and short pulse duration may allow rapidcuring of the lens forming composition without imparting significantradiative heat to the composition.

In an embodiment, controller 990 (shown in FIG. 21) controls theintensity and duration of activating light pulses delivered fromactivating light source 980 and the time interval between pulses, shownin FIG. 19. Activating light source 980 may include capacitor 994, thatstores the energy required to deliver the pulses of activating light.Capacitor 994 may be adapted to allow pulses of activating light to bedelivered as frequently as desired. Temperature monitor 997 may belocated at a number of positions within mold chamber 984. Thetemperature monitor may measure the temperature within the chamberand/or the temperature of air exiting the chamber. The system may beconfigured to send a signal to cooler 988 and/or distributor 986 (shownin FIG. 19) to vary the amount and/or temperature of the cooling air.The temperature monitor may also determine the temperature at any of anumber of locations proximate the mold cavity and send a signal tocontroller 990 to vary the pulse duration, pulse intensity, or timebetween pulses as a function of a temperature within mold chamber 984.

In an embodiment, light sensor 999 may be used to determine theintensity of activating light emanating from source 980. The lightsensor is preferably configured to send a signal to controller 990, thatis preferably configured to maintain the intensity of the activatinglight at a selected level. Filter 998 may be positioned betweenactivating light source 980 and light sensor 999 and is preferablyconfigured to inhibit non-activating light rays from contacting lightsensor 999, while allowing activating rays to contact the sensor. In oneembodiment, the filter may include 365 N glass or any other materialadapted to filter non-activating light (e.g., visible light) andtransmit activating light.

In an embodiment, more than one activating light source may be used tosimultaneously apply activating pulses to the lens forming composition.Such an embodiment is shown in FIG. 20. Activating light sources 980 aand 980 b may be positioned around mold chamber 985 so that pulses maybe directed toward the front face of a lens and the back face of a lenssubstantially simultaneously. Mold chamber 985 is preferably adapted tohold a mold in a vertical position such that pulses from activatinglight source 980 a may be applied to the face of a first mold member,while pulses from activating light source 980 b may be applied to theface of a second mold member. In an embodiment, activating light source980 b applies activating light pulses to a back surface of a lens morefrequently than xenon source 980 a applies activating light pulses to afront surface of a lens. Activating light sources 980 a and 980 b may beconfigured such that one source applies light to mold chamber 984 from aposition above the chamber while the other activating light sourceapplies light to the mold chamber from a position below the chamber.

In an embodiment, a xenon light source and a relatively low intensity(e.g., fluorescent) light source may be used to simultaneously applyactivating light to a mold chamber. As illustrated in FIG. 19, xenonsource 980 may apply activating light to one side of mold chamber 984while low intensity fluorescent source 982 applies activating light toanother side of the mold chamber. Fluorescent source 982 may include acompact fluorescent “light bucket” or a diffused fluorescent lamp. Thefluorescent light source may deliver continuous or substantially pulsedactivating light as the xenon source delivers activating light pulses.The fluorescent source may deliver continuous activating light rayshaving a relatively low intensity of less than about 100 microwatts/cm².

In one embodiment, an upper light filter 254 may be positioned betweenupper light source 214 and lens drawer assembly 216, as depicted in FIG.5. A lower light filter 256 may be positioned between lower light source218 and lens drawer assembly 216. The upper light filter 254 and lowerlight filter 256 are shown in FIG. 5 as being made of a single filtermember, however, those of ordinary skill in the art will recognize thateach of the filters may include two or more filter members. Thecomponents of upper light filter 254 and lower light filter 256 arepreferably modified depending upon the characteristics of the lens to bemolded. For instance, in an embodiment for making negative lenses, theupper light filter 254 includes a plate of Pyrex glass that may befrosted on both sides resting upon a plate of clear Pyrex glass. Thelower light filter 256 includes a plate of Pyrex glass, frosted on oneside, resting upon a plate of clear Pyrex glass with a device forreducing the intensity of activating light incident upon the centerportion relative to the edge portion of the mold assembly.

Conversely, in a preferred arrangement for producing positive lenses,the upper light filter 254 includes a plate of Pyrex glass frosted onone or both sides and a plate of clear Pyrex glass resting upon theplate of frosted Pyrex glass with a device for reducing the intensity ofactivating light incident upon the edge portion in relation to thecenter portion of the mold assembly. The lower light filter 256 includesa plate of clear Pyrex glass frosted on one side resting upon a plate ofclear Pyrex glass with a device for reducing the intensity of activatinglight incident upon the edge portion in relation to the center portionof the mold assembly. In this arrangement, in place of a device forreducing the relative intensity of activating light incident upon theedge portion of the lens, the diameter of the aperture 250 may bereduced to achieve the same result, i.e., to reduce the relativeintensity of activating light incident upon the edge portion of the moldassembly.

It should be apparent to those skilled in the art that each filter 254or 256 could be composed of a plurality of filter members or include anyother means or device effective to reduce the light to its desiredintensity, to diffuse the light and/or to create a light intensitygradient across the mold assemblies. Alternately, in certain embodimentsno filter elements may be used.

In one embodiment, upper light filter 254 or lower light filter 256 eachinclude at least one plate of Pyrex glass having at least one frostedsurface. Also, either or both of the filters may include more than oneplate of Pyrex glass each frosted on one or both surfaces, and/or one ormore sheets of tracing paper. After passing through frosted Pyrex glass,the activating light is believed to have no sharp intensitydiscontinuities. By removing the sharp intensity distributions areduction in optical distortions in the finished lens may be achieved.Those of ordinary skill in the art will recognize that other means maybe used to diffuse the activating light so that it has no sharpintensity discontinuities.

In another embodiment, upper light filter 254 and lower light filter 256may be liquid crystal display (“LCD”) panels. Preferably, the LCD panelis a monochrome trans-flective panel with the back light and reflectorremoved. A monochrome trans-flective LCD panel is manufactured by SharpCorporation and may be purchased from Earth Computer Products. The LCDpanels are preferably positioned such that light from the light sourcespasses through the LCD panels to the lens drawer assembly 216. Theintensity of the light is preferably reduced as the light passes throughthe LCD panel. The LCD panel is preferably programmable such that thelight transmissibility of the LCD panel may be altered. In use, apredetermined pattern of light and dark regions may be displayed on theLCD panel. As light from the light sources hits these regions the lightmay be transmitted through the light regions with a higher intensitythan through the darker regions. In this manner, the pattern of lightand dark areas on the LCD panel may be manipulated such that lighthaving the optimal curing intensity pattern hits the mold assemblies.Although the LCD panel is not entirely opaque in its blackened outstate, it may still reduce the intensity of light reaching the moldassemblies. Typically, the light transmission ratio between the lightestand darkest regions of the LCD panel is about 4 to 1.

The use of an LCD panel as a light filter offers a number of advantagesover the conventional filter systems described earlier. One advantage isthat the filter pattern may be changed actively during a curing cycle.For example, the pattern of light and dark regions may be manipulatedsuch that a lens is initially cured from the center of the lens then thecuring may be gradually expanded to the outer edges of the lens. Thistype of curing pattern may allow a more uniformly cured lens to beformed. In some instances, curing in this manner may also be used toalter the final power of the formed lens.

Another advantage is that the LCD panel may be used as a partial shutterto reduce the intensity of light reaching the mold assembly. Byblackening the entire LCD panel the amount of light reaching any portionof the mold assembly may be reduced. In this manner, the LCD may be usedto create “pulses” of light by alternating between a transmissive anddarkened mode. By having the LCD panel create these light “pulses” aflash ballast or similar pulse generating equipment may be unnecessary.Thus, the light sources may remain on during the entire curing cycle,with the LCD panel creating the curing light pulses. This may alsoincrease the lifetime of the lamps, since the rapid cycling of lampstends to reduce the lamps' lifetime.

In another embodiment, an LCD panel may be used to allow differentpatterns and/or intensities of light to reach two separate moldassemblies. As depicted in FIG. 4, the lens curing unit may beconfigured to substantially simultaneously irradiate two moldassemblies. If the mold assemblies are being used to create lenseshaving the same power the light irradiation pattern and/or intensity maybe substantially the same for each mold assembly. If the mold assembliesare being used to create lenses having significantly different powers,each mold assembly may require a significantly different lightirradiation pattern and/or intensity. The use of an LCD filter may allowthe irradiation of each of the mold assemblies to be controlledindividually. For example, a first mold assembly may require a pulsedcuring scheme, while the other mold assembly may require a continuousirradiation pattern through a patterned filter. The use of an LCD panelmay allow such lenses to be formed substantially simultaneously. A firstportion of the LCD panel between the light source and the first moldingapparatus may be alternatively switched between a darkened and anundarkened state. While a first portion is used to create pulses ofactivating light, another portion of the LCD panel may be formed intothe specific pattern required for the continuous curing of the otherlens.

When non-LCD type filters are used it may be necessary to maintain alibrary of filters for use in the production of different types ofprescription lenses. Typically, each individual prescription will need aparticular filter pattern to obtain a high quality lens. Since an LCDpanel may be programmed into a variety of patterns, it may be possibleto rely on a single LCD panel, rather than a library of filters. The LCDpanel may be programmed to fit the needs of the specific type of lensbeing formed. Such a system also minimizes the need for humanintervention, since a controller may be programmed for a desiredpattern, rather than the operator having to choose among a “library” offilters.

The control of the temperature of an LCD panel filter during a curingcycle may be important for achieving a proper lens. In general as thetemperature of a panel is increased the lighter regions of the panel maybecome darker (i.e., less light transmissive). Thus, it may be necessaryto control the temperature of the LCD panel during curing to ensure thatlight having the appropriate intensity reaches the mold assemblies. Acooling system or heating system may therefore, be coupled to the LCDpanel to ensure proper temperature control. In one embodiment, it ispreferred that a substantially transparent heater is attached to the LCDpanel. By increasing the temperature of the LCD panel the lighttransmissibility of the panel may be decreased. It is preferred that anLCD panel be maintained above room temperature since at room temperaturethe panel may be too light to sufficiently inhibit the light fromreaching the mold assemblies. In order to obtain a proper pattern oflight and dark regions when the LCD panel is heated it may be necessaryto adjust the contrast of the panel. This adjustment may be done eithermanually or electronically.

The LCD panel filters may be coupled to a programmable logic device thatmay be used to design and store patterns for use during curing. FIG.7-10 show a number of patterns which may be generated on an LCD paneland used to filter activating light. Each of these patterns ispreferably used for the production of a lens having a specificprescription power.

As shown in FIG. 11, the mold assembly 352 may include opposed moldmembers 378, separated by an annular gasket 380 to define a lens moldingcavity 382. The opposed mold members 378 and the annular gasket 380 maybe shaped and selected in a manner to produce a lens having a desireddiopter.

The mold members 378 may be formed of any suitable material that willpermit the passage of activating light. The mold members 378 arepreferably formed of glass. Each mold member 378 has an outer peripheralsurface 384 and a pair of opposed surfaces 386 and 388 with the surfaces386 and 388 being precision ground. Preferably the mold members 378 havedesirable activating light transmission characteristics and both thecasting surface 386 and non-casting surface 388 preferably have nosurface aberrations, waves, scratches or other defects as these may bereproduced in the finished lens.

As noted above, the mold members 378 are preferably adapted to be heldin spaced apart relation to define a lens molding cavity 382 between thefacing surfaces 386 thereof. The mold members 378 are preferably held ina spaced apart relation by a T-shaped flexible annular gasket 380 thatseals the lens molding cavity 382 from the exterior of the mold members378. In use, the gasket 380 may be supported on a portion of the moldassembly holder 220 (shown in FIG. 4).

In this manner, the upper or back mold member 390 has a convex innersurface 386 while the lower or front mold member 392 has a concave innersurface 386 so that the resulting lens molding cavity 382 is preferablyshaped to form a lens with a desired configuration. Thus, by selectingthe mold members 378 with a desired surface 386, lenses with differentcharacteristics, such as focal lengths, may be produced.

Rays of activating light emanating from lamps 240 preferably passthrough the mold members 378 and act on a lens forming material disposedin the mold cavity 382 in a manner discussed below so as to form a lens.As noted above, the rays of activating light may pass through a suitablefilter 254 or 256 before impinging upon the mold assembly 352.

The mold members 378, preferably, are formed from a material that willnot transmit activating light having a wavelength below approximately300 nm. Suitable materials are Schott Crown, S-1 or S-3 glassmanufactured and sold by Schott Optical Glass Inc., of Duryea, Pa. orCorning 8092 glass sold by Corning Glass of Corning, N.Y. A source offlat-top or single vision molds may be Augen Lens Co. in San Diego,Calif.

The annular gasket 380 may be formed of vinyl material that exhibitsgood lip finish and maintains sufficient flexibility at conditionsthroughout the lens curing process. In an embodiment, the annular gasket380 is formed of silicone rubber material such as GE SE6035 which iscommercially available from General Electric. In another preferredembodiment, the annular gasket 380 is formed of copolymers of ethyleneand vinyl acetate which are commercially available from E. I. DuPont deNemours & Co. under the trade name ELVAX7. Preferred ELVAX7 resins areELVAX7 350 having a melt index of 17.3-20.9 dg/min and a vinyl acetatecontent of 24.3-25.7 wt. %, ELVAX7 250 having a melt index of 22.0-28.0dg/min and a vinyl acetate content of 27.2-28.8 wt. %, ELVAX7 240 havinga melt index of 38.0-48.0 dg/min and a vinyl acetate content of27.2-28.8 wt. %, and ELVAX7 150 having a melt index of 38.0-48.0 dg/minand a vinyl acetate content of 32.0-34.0 wt. %. In another embodiment,the gasket may be made from polyethylene. Regardless of the particularmaterial, the gaskets 80 may be prepared by conventional injectionmolding or compression molding techniques which are well-known by thoseof ordinary skill in the art.

In another embodiment, FIGS. 32 and 33 present an isometric view and atop view, respectively, of a gasket 510. Gasket 510 may be annular, andis preferably configured to engage a mold set for forming a moldassembly. Gasket 510 is preferably characterized by at least fourdiscrete projections 511. Gasket 510 preferably has an exterior surface514 and an interior surface 512. The projections 511 are preferablyarranged upon inner surface 512 such that they are substantiallycoplanar. The projections are preferably evenly spaced around theinterior surface of the gasket Preferably, the spacing along theinterior surface of the gasket between each projection is about 90degrees. Although four projections are preferred, it is envisioned thatmore than four could be incorporated. The gasket 510 may be formed of asilicone rubber material such as GE SE6035 which is commerciallyavailable from General Electric. In another embodiment, the gasket 510may be formed of copolymers of ethylene and vinyl acetate which arecommercially available from E. I. DuPont de Nemours & Co. under thetrade name ELVAX7. In another embodiment, the gasket 510 may be formedfrom polyethylene.

As shown in FIG. 34, projections 511 are preferably capable of spacingmold members 526 of a mold set. Mold members 526 may be any of thevarious types and sizes of mold members that are well known in the art.A mold cavity 528 at least partially defined by mold members 526 andgasket 510, is preferably capable of retaining a lens formingcomposition. Preferably, the seal between gasket 510 and mold members526 is as complete as possible. The height of each projection 511preferably controls the spacing between mold members 526, and thus thethickness of the finished lens. By selecting proper gaskets and moldsets, lens cavities may be created to produce lenses of various powers.

A mold assembly consists of two mold members. A front mold member 526 aand a back mold member 526 b, as depicted in FIG. 34. The back moldmember is also known as the convex mold member. The back mold memberpreferably defines the concave surface of a convex lens. Referring backto FIGS. 32 and 33, locations where the steep axis 522 and the flat axis524 of the back mold member 526 b preferably lie in relation to gasket510 have been indicated. In conventional gaskets, a raised lip may beused to space mold members. The thickness of this lip varies over thecircumference of the lip in a manner appropriate with the type of moldset a particular gasket is designed to be used with. In order to havethe flexibility to use a certain number of molds, an equivalent amountof conventional gaskets is typically kept in stock.

However, within a class of mold sets there may be points along the outercurvature of a the back mold member where each member of a class of backmold members is shaped similarly. These points may be found at locationsalong gasket 510, oblique to the steep and flat axes of the moldmembers. In a preferred embodiment, these points are at about 45 degreeangles to the steep and flat axes of the mold members. By using discreteprojections 511 to space the mold members at these points, an individualgasket could be used with a variety of mold sets. Therefore, the numberof gaskets that would have to be kept in stock may be greatly reduced.

In addition, gasket 510 may include a recession 518 for receiving a lensforming composition. Lip 520 may be pulled back in order to allow a lensforming composition to be introduced into the cavity. Vent ports 516 maybe incorporated to facilitate the escape of air from the mold cavity asa lens forming composition is introduced.

A method for making a plastic eyeglass lenses using gasket 510 ispresented. The method preferably includes engaging gasket 510 with afirst mold set for forming a first lens of a first power. The first moldset preferably contains at least a front mold member 526 a and a backmold member 526 b. A mold cavity for retaining a lens formingcomposition may be at least partially defined by mold members 526 a and526 b and gasket 510. Gasket 510 is preferably characterized by at leastfour discrete projections 511 arranged on interior surface 512 forspacing the mold members. Engaging gasket 510 with the mold setpreferably includes positioning the mold members such that each of theprojections 511 forms an oblique angle with the steep and flat axis ofthe back mold member 526 b. In a preferred embodiment, this angle isabout 45 degrees. The method preferably further includes introducing alens forming composition into mold cavity 528 and curing the lensforming composition. Curing may include exposing the composition toactivating light and/or thermal radiation. After the lens is cured, thefirst mold set may be removed from the gasket and the gasket may then beengaged with a second mold set for forming a second lens of a secondpower.

FIGS. 35 and 36 present an isometric view and a top view, respectively,of an improved gasket. Gasket 530 may be composed of similar materialsas gasket 510. Like gasket 510, gasket 530 is preferably annular, butmay be take a variety of shapes. In addition, gasket 530 may incorporateprojections 531 in a manner similar to the projections 511 shown in FIG.32. Alternatively, gasket 530 may include a raised lip along interiorsurface 532 or another method of spacing mold members that isconventional in the art.

Gasket 530 preferably includes a fill port 538 for receiving a lensforming composition while gasket 530 is fully engaged to a mold set.Fill port 538 preferably extends from interior surface 532 of gasket 530to an exterior surface 534 of gasket 530. Consequently, gasket 530 neednot be partially disengaged from a mold member of a mold set in order toreceive a lens forming composition. In order to introduce a lens formingcomposition into the mold cavity defined by a conventional mold/gasketassembly the gasket must be at least partially disengaged from the moldmembers. During the process of filling the mold cavity, lens formingcomposition may drip onto the backside of a mold member. Lens formingcomposition on the backside of a mold member may cause activating lightused to cure the lens to become locally focused, and may cause opticaldistortions in the final product. Because fill port 538 allows lensforming composition to be introduced into a mold cavity while gasket 530is fully engaged to a mold set, gasket 530 preferably avoids thisproblem. In addition, fill port 538 may be of sufficient size to allowair to escape during the introduction of a lens forming composition intoa mold cavity; however, gasket 530 may also incorporate vent ports 536to facilitate the escape of air.

A method for making a plastic eyeglass lens using gasket 530 preferablyincludes engaging gasket 530 with a first mold set for forming a firstlens of a first power. The first mold set preferably contains at least afront mold member and a back mold member. A mold cavity for retaining alens forming composition may be at least partially defined by the frontmold member, the back mold member, and the gasket. Preferably, themethod further includes introducing a lens forming composition throughfill port 538, wherein the first and second mold members remain fullyengaged with the gasket during the introduction of the lens formingcomposition. The lens forming composition may then be cured by use ofactivating light and/or thermal radiation.

In operation, the apparatus may be appropriately configured for theproduction of positive lenses which are relatively thick at the centeror negative lenses which are relatively thick at the edge. To reduce thelikelihood of premature release, the relatively thick portions of a lensare preferably polymerized at a faster rate than the relatively thinportions of a lens.

The rate of polymerization taking place at various portions of a lensmay be controlled by varying the relative intensity of activating lightincident upon particular portions of a lens. The rate of polymerizationtaking place at various portions of a lens may also be controlled bydirecting air across the mold members 378 to cool the mold assembly 352.

For positive lenses, the intensity of incident activating light ispreferably reduced at the edge portion of the lens so that the thickercenter portion of the lens polymerizes faster than the thinner edgeportion of the lens. Conversely, for a negative lens, the intensity ofincident activating light is preferably reduced at the center portion ofthe lens so that the thicker edge portion of the lens polymerizes fasterthan the thinner center portion of the lens. For either a positive lensor a negative lens, air may be directed across the faces of the moldmembers 378 to cool the mold assembly 352. As the overall intensity ofincident activating light is increased, more cooling is needed which maybe accomplished by either or both of increasing the velocity of the airand reducing the temperature of the air.

It is well known by those of ordinary skill in the art that lens formingmaterials tend to shrink as they cure. If the relatively thin portion ofa lens is allowed to polymerize before the relatively thick portion, therelatively thin portion will tend to be rigid at the time the relativelythick portion cures and shrinks and the lens will either releaseprematurely from or crack the mold members. Accordingly, when therelative intensity of activating light incident upon the edge portion ofa positive lens is reduced relative to the center portion, the centerportion may polymerize faster and shrink before the edge portion isrigid so that the shrinkage is more uniform. Conversely, when therelative intensity of activating light incident upon the center portionof a negative lens is reduced relative to the edge portion, the edgeportion may polymerize faster and shrink before the center becomes rigidso that the shrinkage is more uniform.

The variation of the relative intensity of activating light incidentupon a lens may be accomplished in a variety of ways. According to onemethod, in the case of a positive lens, a ring of opaque material may beplaced between the lamps and the mold assembly so that the incidentactivating light falls mainly on the thicker center portion of the lens.Alternatively, when an LCD panel is used as the filter, the panel may beprogrammed to form a pattern so that the incident activating light fallsmainly on the thicker center portion of the lens (See FIG. 7, patternsA, B, C, D, F, H, and I). Conversely, for a negative lens, a disk ofopaque material may be placed between the lamps 240 and the moldassembly 352 so that the incident activating light falls mainly on theedge portion of the lens. Alternatively, when an LCD panel is used asthe filter, the panel may be programmed to form a pattern so that theincident activating light falls mainly on the thicker edge portion ofthe lens (See FIG. 9, patterns C, F, I, and FIG. 10, patterns A, B, D,E, G, and H).

According to another method, in the case of a negative lens, a sheetmaterial or an LCD panel having a pattern with a variable degree ofopacity ranging from opaque at a central portion to transparent at aradial outer portion may be disposed between the lamps 240 and the moldassembly 352. Conversely, for a positive lens, a sheet material or LCDpanel having a pattern with a variable degree of opacity ranging fromtransparent at a central portion to opaque at a radial outer portion maybe disposed between the lamps 240 and the mold assembly 352.

As noted above, the mold assembly 352 may be cooled during curing of thelens forming material as the overall intensity of the incidentactivating light is increased. Cooling of the mold assembly 352generally reduces the likelihood of premature release by slowing thereaction and improving adhesion. There may also be improvements in theoptical quality, stress characteristics and impact resistance of thelens. Cooling of the mold assembly 352 is preferably accomplished byblowing air across the mold assembly 352. The air preferably has atemperature ranging between 15 and 85° F. (about −9.4° C. to 29.4° C.)to allow for a curing time of between 30 and 10 minutes. The airdistribution devices have been found to be particularly advantageous asthey may be specifically designed to direct air directly across thesurface of the opposed mold members 378. After passing across thesurface of the opposed mold members 378, the air emanating from the airdistribution devices may be vented out of the system. Alternately theair emanating from the air distribution devices may be recycled back toan air cooler. In another embodiment, the mold assembly 352 may also becooled by disposing the mold assembly in a liquid cooling bath.

The opposed mold members 378 are preferably thoroughly cleaned betweeneach curing run as any dirt or other impurity on the mold members 378may cause premature release. The mold members 378 may be cleaned by anyconventional means well known to those of ordinary skill in the art suchas with a domestic cleaning product, i.e., Mr. Clean™ available fromProctor and Gamble. Those of ordinary skill in the art will recognize,however, that many other techniques may also be used for cleaning themold members 378.

After curing of the lens in lens curing unit 30, the lens may bede-molded and post-cured in the post-cure unit 40. Post-cure unit 40 ispreferably configured to apply light, heat or a combination of light andheat to the lens. As shown in FIG. 12, post-cure unit 40 may include alight source 414, a lens drawer assembly 416, and a heat source 418.Lens drawer assembly 416 preferably includes a lens holder 420, morepreferably at least two lens holders 420. Lens drawer assembly 416 ispreferably slidingly mounted on a guide. Preferably, lens drawerassembly 416 is made from a ceramic material. Cured lenses may be placedin lens holders 420 while the lens drawer assembly 416 is in the openposition (i.e., when the door extends from the front of post-cure unit40). After the lenses have been loaded into lens holders 420 the doormay be slid into a closed position, with the lenses directly under lightsource 414 and above heat source 418.

As shown in FIG. 12, it is preferred that the light source 414 includesa plurality of light generating devices or lamps 440. Preferably, lamps440 may be oriented above each of the lens holders when the lens drawerassembly is closed. The lamps 440, preferably, generate activatinglight. The lamps 440 may be supported by and electrically connected tosuitable fixtures 442. The fixtures may be at least partially reflectiveand concave in shape to direct light from the lamps 440 toward the lensholders. The lamps may generate either ultraviolet light, actinic light,visible light, and/or infrared light. The choice of lamps is preferablybased on the monomers used in the lens forming composition. In oneembodiment, the activating light may be generated from a fluorescentlamp. The fluorescent lamp preferably has a strong emission spectra fromabout 200 nm to about 800 nm, more preferably between about 200 nm toabout 400 nm. A fluorescent lamp emitting activating light with thedescribed wavelengths is commercially available from Phillips as modelPL-S 9W/10. In another embodiment, the lamp may generate ultravioletlight.

In one embodiment, the activating light source may be turned on and offquickly between exposures. A flasher ballast may be used for thisfunction. The flasher ballast may be positioned beneath the post-cureunit. A flasher ballast may operate in a standby mode wherein a lowcurrent is preferably supplied to the lamp filaments to keep thefilaments warm and thereby reduce the strike time of the lamp. Such aballast is commercially available from Magnatek, Inc of Bridgeport,Conn.

Heat source 418 may be configured to heat the interior of the post-cureunit. Preferably, heat source 418 is a resistive heater. Heat source 418may be made up of one or two resistive heaters. The temperature of heatsource 418 may be thermostatically controlled. By heating the interiorof the post-cure unit the lenses which are placed in post-cure unit 40may be heated to complete curing of the lens forming material. Post-cureunit 40 may also include a fan to circulate air within the unit. Thecirculation of air within the unit may help maintain a relativelyuniform temperature within the unit. The fan may also be used to coolthe temperature of post-cure unit 40 after completion of the post cureprocess.

In an embodiment, described as follows, a lens cured by exposure toactivating light may be further processed by conductive heating. Suchconductive heating tends to enhance the degree of cross-linking in thelens and to increase the tintability of the lens. A lens formingmaterial is preferably placed in mold cavity 900 (illustrated in FIG.16), which is defined by at least first mold member 902 and second moldmember 904. Activating light is directed toward at least one of the moldmembers, thereby curing the lens forming material to a lens. Heatdistributor 910 (shown in FIG. 13) may be adapted to distributeconductive heat from conductive heat source 418 to at least one moldmember. Heat distributor 910 is preferably flexible such that at least aportion of it may be shaped to substantially conform to the shape offace 906 or face 907 of first mold member 902 or second mold member 904,respectively. Heat distributor 910 is preferably placed in contact withconductive heat source 418, and mold member 902 is preferably placed onheat distributor 910 such that face 906 of the mold member rests on topof the heat distributor 910. Heat distributor 910 may be coupled to heatsource 418. Heat is preferably conductively applied to the heatdistributor 910 by the heat source 418. Heat is preferably conductedfrom the heat distributor 910 through the mold member to a face of thelens. The heat distributor may be shaped to accommodate face 906 offirst mold member 902 or face 907 of second mold member 904 such thatthe heat is applied to front face 916 or back face 915 of the lens. Thetemperature of heat source 418 may be thermostatically controlled.

In an embodiment, a resistive heater 418 (shown in FIG. 17) may be usedas a heat source to provide conductive heat to the lens. A number ofother heat sources may be used. In an embodiment, heat distributor 910may include countershape 920. Countershape 920 may be placed on top ofthe hot plate to distribute conductive heat from the hot plate. Thecountershape is preferably flexible such that at least a portion of itmay substantially conform to the shape of an outside face of a moldmember. The countershape may be hemispherical and either convex orconcave depending upon whether the surface of the mold assembly to beplaced upon it is convex or concave. For example, when the concavesurface of the back mold is utilized to conduct heat into the lensassembly, a convex countershape is preferably provided to rest theassembly on.

Countershape 920 may include a glass mold, a metal optical lap, a pileof hot salt and/or sand, or any of a number of other devices adapted toconduct heat from heat source 912. It should be understood that FIG. 17includes combinations of a number of embodiments for illustrativepurposes. Any number of identical or distinct countershapes may be usedin combination on top of a heat source. In an embodiment, a countershapeincludes a container 922 filled with particles 924. The particlespreferably include metal or ceramic material. Countershape 920 mayinclude heat distributor 910. A layer 914 of material may be placed overthe countershape 920 or heat distributor 910 to provide slow, smooth,uniform heat conduction into the lens mold assembly. This layerpreferably has a relatively low heat conductivity and may be made ofrubber, cloth, Nomex™ fabric or any other suitable material thatprovides slow, smooth, uniform conduction.

In an embodiment, countershape 920 includes layer 914 (e.g., a bag orcontainer) filled with particles 924 such that the countershape may beconveniently shaped to conform to the shape of face 906 or face 907. Inan embodiment, the countershape is preferably a “beanbag” that containsparticles 924 and may be conformable to the shape of a mold face placedon top of it. Particles 924 may include ceramic material, metalmaterial, glass beads, sand and/or salt. The particles preferablyfacilitate conductive heat to be applied to face 906 or face 907substantially evenly.

In an embodiment, the countershape 920 is preferably placed on top ofheat source 418. Countershape 920 is preferably heated until thetemperature of the countershape is substantially near or equal to thetemperature of the surface of the heat source. The countershape may thenbe “flipped over” such that the heated portion of the countershape thathas a temperature substantially near or equal to that of the surface ofthe heat source is exposed. A mold may be placed on top of the heatedportion of the countershape, and the countershape is preferablyconformed to the shape of the face of the mold. In this manner, the rateof conductive heat transfer to the lens may begin at a maximum. Heat ispreferably conductively transferred through the countershape and themold face to a face of the lens. The temperature of the heated portionof the countershape may tend to decrease after the mold is placed ontothe countershape.

In an embodiment, heat distributor 910 may partially insulate a moldmember from conductive heat source 418. The heat distributor preferablyallows a gradual, uniform transfer of heat to the mold member. The heatdistributor is preferably made of rubber and/or another suitablematerial. The heat distributor may include countershapes of variousshapes (e.g., hemispherically concave or convex) and sizes that may beadapted to contact and receive mold members.

In an embodiment, heat may be conductively applied by the heat source toonly one outside face of one mold member. This outside face may be face906 or face 907. Heat may be applied to the back face of the lens toenhance crosslinking and/or tintability of the lens material proximateto the surface of the back face of the lens.

In a preferred embodiment, a thermostatically controlled hot plate 418is preferably used as a heat source. Glass optical mold 928 ispreferably placed convex side up on hot plate 418 to serve as acountershape. The glass optical mold preferably has about an 80 mmdiameter and a radius of curvature of about 93 mm. Rubber disc 929 maybe placed over this mold 928 to provide uniform conductive heat to thelens mold assembly. The rubber disc is preferably made of silicone andpreferably has a diameter of approximately 74 mm. and a thickness ofabout 3 mm. The lens mold assembly is preferably placed on mold 928 sothat outside face 906 of a mold member of the assembly rests on top ofmold 928. It is preferred that the edge of the lens mold assembly notdirectly contact the hot plate. The lens mold assembly preferablyreceives heat through the rubber disc and not through its mold edges.

To achieve good yield rates and reduce the incidence of prematurerelease while using the conductive heat method, it may be necessary forthe edge of the lens to be completely cured and dry before conductiveheat is applied. If the lens edge is incompletely cured (i.e., liquid orgel is still present) while conductive heat is applied, there may be ahigh incidence of premature release of the lens from the heating unit.

In an embodiment, the edges of a lens may be treated to cure or removeincompletely cured lens forming material (see above description) beforeconductive heat is applied. The mold cavity may be defined by at leastgasket 908, first mold member 902, and second mold member 904.Activating light rays may be directed toward at least one of the moldmembers, thereby curing the lens forming material to a lens preferablyhaving front face 916, a back face 915, and edges. Upon the formation ofthe lens, the gasket may be removed from the mold assembly. An oxygenbarrier may be used to cure any remaining liquid or gel on the lens edgeas described in more detail below. An oxygen barrier treated withphotoinitiator is preferably employed. Alternatively, any remainingliquid or gel may be removed manually. Once the edge of the lens is dry,a face of the lens may be conductively heated using any of the methodsdescribed herein.

In an embodiment, a lens may be tinted after receiving conductive heatpostcure treatment in a mold cavity. During tinting of the lens, thelens is preferably immersed in a dye solution.

The operation of the lens curing system may be controlled by amicroprocessor based controller 50 (FIG. 1). Controller 50 preferablycontrols the operation of coating unit 20, lens curing unit 30, andpost-cure unit 40. Controller 50 may be configured to substantiallysimultaneously control each of these units. In addition, the controllermay include a display 52 and an input device 54. The display and inputdevice may be configured to exchange information with an operator.

Controller 50 preferably controls a number of operations related to theprocess of forming a plastic lens. Many of the operations used to make aplastic lens (e.g., coating, curing and post-cure operations) arepreferably performed under a predetermined set of conditions based onthe prescription and type of lens being formed (e.g.,ultraviolet/visible light absorbing, photochromic, colored, etc.).Controller 50 is preferably programmed to control a number of theseoperations, thus relieving the operator from having to continuallymonitor the apparatus.

In some embodiments, the lens or mold members may be coated with avariety of coatings (e.g., a scratch resistant or tinted coating). Theapplication of these coatings may require specific conditions dependingon the type of coating to be applied. Controller 50 is preferablyconfigured to produce these conditions in response to input from theoperator.

When a spin coating unit is used, controller 50 may be configured tocontrol the rotation of the lens or mold member during the coatingprocess. Controller 50 is preferably electronically coupled to the motorof the spin coating unit. The controller may send electronic signals tothe motor to turn the motor on and/or off. In a typical coating processthe rate at which the mold or lens is rotated is preferably controlledto achieve a uniform and defect free coating. The controller ispreferably configured to control the rate of rotation of the mold orlens during a curing process. For example, when a coating material isbeing applied, the mold or lens is preferably spun at relatively highrotational rates (e.g., about 900 to about 950 RPM). When the coatingmaterial is being cured, however, a much slower rotational rate ispreferably used (e.g., about 200 RPM). The controller is preferablyconfigured to adjust the rotational rate of the lens or mold dependingon the process step being performed.

The controller is also preferably configured to control the operation oflamps 24. The lamps are preferably turned on and off at the appropriatetimes during a coating procedure. For example, during the application ofthe coating material activating lights are typically not used, thus thecontroller may be configured to keep the lamps off during this process.During the curing process, activating light may be used to initiate thecuring of the coating material. The controller is preferably configuredto turn the lamps on and to control the amount of time the lamps remainon during a curing of the coating material. The controller may also beconfigured to create light pulses to affect curing of the coatingmaterial. Both the length and frequency of the light pulses may becontrolled by the controller.

The controller is also preferably configured to control operation of thelens-curing unit. The controller may perform some and/or all of a numberof functions during the lens curing process, including, but not limitedto: (i) measuring the ambient room temperature; (ii) determining thedose of light (or initial dose of light in pulsed curing applications)required to cure the lens forming composition, based on the ambient roomtemperature; (iii) applying the activating light with an intensity andduration sufficient to equal the determined dose; (iv) measuring thecomposition's temperature response during and subsequent to theapplication of the dose of light; (v) calculating the dose required forthe next application of activating light (in pulsed curingapplications); (vi) applying the activating light with an intensity andduration sufficient to equal the determined second dose; (vii)determining when the curing process is complete by monitoring thetemperature response of the lens forming composition during theapplication of activating light; (viii) turning the upper and lowerlight sources on and off independently; (ix) monitoring the lamptemperature, and controlling the temperature of the lamps by activatingcooling fans proximate the lamps; and (x) turning the fans on/off orcontrolling the flow rate of an air stream produced by a fan to controlthe composition temperature. Herein, “dose” refers to the amount oflight energy applied to an object, the energy of the incident lightbeing determined by the intensity and duration of the light.

A temperature monitor may be located at a number of positions within thelens curing unit 30. In one embodiment an infra-red temperature sensormay be located such that it may measure the temperature of the moldand/or the lens forming composition in the mold cavity. One infra-redtemperature sensor may be the Cole-Parmer Model E39669-00 (Vernon Hills,Ill.).

The temperature monitor may measure the temperature within the chamberand/or the temperature of air exiting the chamber. The controller may beconfigured to send a signal to a cooler and/or distributor to vary theamount and/or temperature of the cooling air. The temperature monitormay also determine the temperature at any of a number of locationsproximate the mold cavity. The temperature monitor preferably sends asignal to the controller such that the temperature of the mold cavityand/or the lens forming composition may be relayed to the controllerthroughout the curing process.

During the initial set-up of a curing process the temperature of thelens forming composition within the mold cavity may be determined. Thisinitial temperature of the lens forming composition may be about equalto the ambient room temperature. The controller may then determine theinitial temperature of the lens forming composition by measuring theambient room temperature. Alternatively, the initial temperature of thelens forming composition may be measured directly using theaforementioned temperature sensors.

The controller preferably determines the initial dose to be given to thelens forming composition based on the initial temperature of thecomposition. The controller may use a table to determine the initialdose, the table including a series of values correlating the initialtemperature to the initial dose and/or the mass of the lens formingcomposition. The table may be prepared by routine experimentation. Toprepare the table a specific lens forming composition of a specific massis preferably treated with a known dose of activating light. The moldcavity is preferably disassembled and the gelation pattern of the lensforming composition observed. This procedure may be repeated, increasingor decreasing the dosage as dictated by the gelation patterns, until theoptimal dosage is determined for the specific lens forming composition.

During this testing procedure the initial temperature of the lensforming composition may be determined, this temperature being hereinreferred to as the “testing temperature”. In this manner, the optimaldose for the lens forming composition at the testing temperature may bedetermined. When the lens forming material has an initial temperaturethat is substantially equal to the testing temperature, the initialdosage may be substantially equal to the experimentally determineddosage. When the lens forming material has a temperature that issubstantially greater or less than the testing temperature, the initialdose may be calculated based on a function of the experimentallydetermined initial dose. In single dose applications the initial dose ofactivating light will be sufficient to substantially cure the plasticlens. For multi-pulse applications, the initial dose will be followed byadditional light doses.

In an embodiment, the controller is preferably adapted to control theintensity and duration of activating light pulses delivered from theactivating light source and the time interval between the pulses. Theactivating light source may include a capacitor which stores the energyrequired to deliver the pulses of activating light. The capacitor mayallow pulses of activating light to be delivered as frequently asdesired. A light sensor may be used to determine the intensity ofactivating light emanating from the source. The light sensor ispreferably adapted to send a signal to the controller, which ispreferably adapted to maintain the intensity of the activating light ata selected level. A filter may be positioned between the activatinglight source and the light sensor and is preferably adapted to inhibit aportion of the activating light rays from contacting the light sensor.This filter may be necessary to keep the intensity of the activatinglight upon the light sensor within the detectable range of the lightsensor.

In an embodiment, a shutter system may be used to control theapplication of activating light rays to the lens forming material. Theshutter system preferably includes air-actuated shutter plates that maybe inserted into the curing chamber to prevent activating light fromreaching the lens forming material. The shutter system may be coupled tothe controller, which may actuate an air cylinder to cause the shutterplates to be inserted or extracted from the curing chamber. Thecontroller preferably allows the insertion and extraction of the shutterplates at specified time intervals. The controller may receive signalsfrom temperature sensors allowing the time intervals in which theshutters are inserted and/or extracted to be adjusted as a function of atemperature of the lens forming composition and/or the molds. Thetemperature sensor may be located at numerous positions proximate themold cavity and/or casting chamber.

Alternatively, the shutter system may include an LCD filter that may bedarkened to inhibit the activating light from reaching the lens formingmaterial. The controller is preferably configured to darken the LCDpanel at specified time intervals. The controller may receive signalsfrom temperature sensors allowing the time intervals in which the LCDpanel is darkened to be adjusted as a function of a temperature of thelens forming composition and/or the molds.

In an embodiment, a single dose of activating light may be used to curea lens forming composition. The controller may monitor the change intemperature of the lens forming composition during the application ofactivating light. The activating light preferably initiates apolymerization reaction such that the temperature of the lens formingcomposition begins to rise. By monitoring the change in temperature overa time period the controller may determine the rate of temperaturechange. The controller preferably controls the polymerization of thelens forming composition based on the rate of temperature change. Whenthe temperature is found to be rising at a faster than desired rate, thedesired rate being determined based on previous experiments, thetemperature controller may alter the intensity and/or the duration ofthe pulse such that the rate of temperature change is lowered. Theduration of the activating light may be shortened and/or the intensityof the activating light may be diminished to achieve this effect. Thecontroller may also increase the rate of cooling air blowing across themold to help lower the temperature of the lens forming composition.Alternatively, if the temperature of the reaction is increasing tooslowly, the controller may increase the intensity of the activatinglight and/or increase the duration of the pulse. Additionally, thecontroller may decrease the rate of cooling air blowing across the moldto allow the temperature of the lens forming composition to rise at afaster rate.

One manner in which the temperature may be controlled is by monitoringthe temperature during the application of activating light, as describedin U. S. Pat. No. 5,422,046 to Tarshiani, et al. During activating lightirradiation, the temperature of the lens forming composition tends torise. When the temperature reaches a predetermined upper set point theactivating light source is preferably turned off. Removal of theactivating energy may allow the temperature to gradually begin to fall.When the temperature is reduced to a predetermined lower set point theactivating light source is preferably turned on. In this manner, thetemperature may be controlled within a desired range. This temperaturerange tends to be very broad due to the nature of the lens formingpolymerization reactions. For example, turning the activating light offat a predetermined upper set point may not insure that the temperatureof the lens forming composition will stop at that point. In fact, it ismore likely that the temperature may continue to rise after the upperset point has been reached. To offset this effect the upper set pointmay be set at a temperature lower than the upper temperature desiredduring the lens forming process. Such a method of temperature controlmay be insufficient to control the temperature. As shown in FIG. 17,increase in the temperature of a lens forming composition during thelens forming process may not be constant. Since the increase intemperature of the composition changes as the process continues, the useof an upper set point for controlling the temperature may not adequatelyprevent the composition from reaching greater than desired temperatures.Additionally, near the completion of the process the upper set point maybe set too low, thereby preventing the lens forming composition fromreaching a temperature that is adequate to maintain the polymerizationreaction due to insufficient doses of activating light.

In an embodiment the temperature control process may be described as amodified Proportional-Integral-Derivative (“PID”) control method.Preferably, the controller is configured to operate the lens-curingsystem using a PID control method. The controller may use a number offactors to determine the dose of activating light applied for eachpulse. The controller preferably measures the temperature as well as therate of temperature change.

The PID control method involves the combination of proportional,integral and derivative controlling methods. The first, proportionalcontrol, may be achieved by mixing two control factors in such a way asto achieve the desired effect. For lens control the two factors whichtend to have the most effect on temperature control may be the dosage ofactivating light and the flow rate of the cooling air. These two factorsmay be altered to achieve a desired temperature response. If thetemperature must be raised as rapidly as possible a full dosage of lightmay delivered with no cooling air present. Similarly, if the compositionmust be rapidly cooled the sample may be treated with cooling air only.Preferably the two factors, application of incident light and cooling,are preferably both applied to achieve the desired temperature response.The mixture, or proportions of these factors may allow the temperatureof the composition to be controlled.

The use of proportional control tends to ignore other effects thatinfluence the temperature of the lens forming composition. During thelens forming process, the temperature of the lens forming compositionmay vary due to the rate of polymerization of the reaction. When thecomposition is undergoing a rapid rate of polymerization, thetemperature of the composition may rise beyond that determined by theproportional setting of the activating light and cooling air controls.Toward the end of the process the lens may become too cool due to the areduction in the rate of polymerization of the composition. The use ofproportional control may therefore be inadequate to control thisprocedure and may lead to greater than desired variations in thetemperature of the composition.

These limitations may be overcome by altering the proportions of the twocomponents in response to the temperature of the composition. A singleset point may be used to control the temperature of a reaction. As thetemperature rises above this set point the proportion of the activatinglight and cooling may be adjusted such that the temperature begins tolower back toward the set point. If the temperature drops below the setpoint the proportion of activating light and cooling may be adjusted toraise the temperature back to the set point. Typically, to lower thetemperature the dose of activating light may be reduced and/or the flowrate of the cooling air may be increased. To raise the temperature thedose of activating light may be increased and/or the flow rate of thecooling air may be decreased.

The use of proportional control in this manner may not lead to a steadytemperature. Depending on the set point and the response time of thelens forming composition to variations in the dosage of light and/orcooling air, the temperature may oscillate over the set point, neverattaining a steady value. To better control such a system the rate ofchange of the temperature over a predetermined time period is preferablymonitored. As the temperature rises the rate at which the temperaturerises is preferably noted. Based on this rate of change the controllermay then alter the dosage of activating light and/or cooling air suchthat a temperature much closer to the set point may be achieved. Sincethe rate will change in response to changes in the rate ofpolymerization, such a system may better control the temperature of thelens forming composition throughout the process.

In an embodiment, the controller may be a modified PID controller or acomputer programmed to control the lens curing unit using a PID controlscheme. The controller preferably monitors the temperature of the lensforming composition throughout the process. Additionally, the controllermay monitor the rate of change of temperature throughout the reaction.When a plurality of pulses are being applied to control thepolymerization, the controller preferably controls the duration andintensity of each pulse to control the temperature of the composition.In a typical process the rate of change in temperature is preferablymonitored after the application of an activating light pulse. If thetemperature is trending in an upward direction, the controllerpreferably waits for the temperature to crest and start descending,before the application of additional light pulses. This crestingtemperature may vary, as depicted in FIG. 17, throughout the lensforming process. After the temperature has passed a predetermined setpoint, a dose, calculated from the rate of change in temperature causedby the application of the previous pulse, may be applied to the lensforming composition. After the light pulse is delivered the controllermay repeat the procedure additional times.

When the reaction nears completion the controller detects the lack ofresponse to the last exposure (i.e. the lens temperature did notincrease appreciably). At this point the controller may apply a finaldose to assure a substantially complete cure and notify the operatorthat the mold assembly is ready to be removed form the chamber.

One method of controlling the dose of light reaching the lens may bethrough the use of filters, as described above. In one embodiment, anLCD filter system may be used to adjust the intensity of incoming light.The LCD system is preferably coupled to the controller such that apattern displayed by the LCD system may be altered by the controller.The controller preferably configures the pattern of light and dark areason the LCD panel such that light having the optimal curing intensitypattern hits the mold assemblies. The pattern that is produced ispreferably based on the prescription and type of lens being produced.

In another embodiment, the controller may actively change the pattern onthe LCD panel during a curing cycle. For example, the pattern of lightand dark regions may be manipulated such that the lens is cured from thecenter of the lens then gradually expanded to the outer edges of thelens. This type of curing pattern may allow a more uniformly cured lensto be formed. In some instances, curing in this manner may also be usedto alter the final power of the formed lens.

In another embodiment, the LCD panel may be used as a partial shutter toreduce the intensity of light reaching the lens assembly. By blackeningthe entire LCD panel the amount of light reaching any portion of themold assembly may be reduced. The controller may be configured to causethe LCD panel to create “pulses” of light by alternating between atransmissive and darkened mode. By having the LCD panel create theselight “pulses” the need for a flash ballast or similar pulse generatingequipment may be unnecessary. Thus the use of a controller and an LCDpanel may simplify the system.

In some embodiments, the lens may require a post-curing process. Thepost-cure process may require specific conditions depending on the typeof lens being formed. The controller is preferably configured to producethese conditions in response to input from the operator.

The controller is preferably configured to control the operation oflamps 440 (See FIG. 12). The lamps are preferably turned on and off atthe appropriate times during the post-cure procedure. For example, insome post-cure operations the lights may not be required, thus thecontroller would keep the lights off during this process. During otherprocesses, the lights may be used to complete the curing of the lens.The controller is preferably configured to turn the lights on and tocontrol the amount of time the lights remain on during a post-cureprocedure. The controller may also be configured to create light pulsesduring the post-cure procedure. Both the length and frequency of thelight pulses may be controlled by the controller.

The controller is preferably configured to control operation of theheating device 418 during the post-cure operation. Heating device 418 ispreferably turned on and off to maintain a predetermined temperaturewithin the post-cure unit. Alternatively, when a resistive heater isused, the current flow through the heating element may be altered tocontrol the temperature within the post-cure unit. Preferably both theapplication of light and heat are controlled by the controller. Theoperation of fans, coupled to the post-cure unit, is also preferablycontrolled by the controller. The fans may be operated by the controllerto circulate air within or into/out of the post-cure unit.

Additionally, the controller may provide system diagnostics to determineif the system is operating properly. The controller may notify the userwhen routine maintenance is due or when a system error is detected. Forexample, the controller may monitor the current passing through lamps ofthe coating, lens curing, or post-cure unit to determine if the lampsare operating properly. The controller may keep track of the number ofhours that the lamps have been used. When a lamp has been used for apredetermined number of hours a message may be transmitted to anoperator to inform the operator that the lamps may require changing. Thecontroller may also monitor the intensity of light produced by the lamp.A photodiode may be placed proximate the lamps to determine theintensity of light being produced by the lamp. If the intensity of lightfalls outside a predetermined range, the current applied to the lamp maybe adjusted to alter the intensity of light produced (either increasedto increase the intensity; or decreased to decrease the intensity).Alternatively, the controller may transmit a message informing theoperator that a lamp needs to be changed when the intensity of lightproduced by the lamp drops below a predetermined value.

The controller may also manage an interlock system for safety and energyconservation purposes. If the lens drawer assembly from the coating orpost-cure units are open the controller is preferably configured toprevent the lamps from turning on. This may prevent the operator frominadvertently becoming exposed to the light from the lamps. Lamps 24 forthe coating unit 20 are preferably positioned on cover 22 (See FIG. 1).In order to prevent inadvertent exposure of the operator to light fromlamps 24 a switch is preferably built into the cover, as describedabove. The controller is preferably configured to prevent the lamps 24from turning on when the cover is open. The controller may alsoautomatically turn lamps 24 off if the cover is opened when the lensesare on. Additionally, the controller may conserve energy by keeping fansand other cooling devices off when the lamps are off.

The controller may also be configured to interact with the operator. Thecontroller preferably includes an input device 54 and a display screen52. The input device may be a keyboard (e.g., a full computer keyboardor a modified keyboard), a light sensitive pad, a touch sensitive pad,or similar input device. A number the parameters controlled by thecontroller may be dependent on the input of the operator. In the initialset up of the apparatus, the controller may allow the operator to inputthe type of lens being formed. This information may include type of lens(clear, ultraviolet absorbing, photochromic, colored, etc.),prescription, and type of coatings (e.g., scratch resistant or tint).

Based on this information the controller is preferably configured totransmit information back to the operator. The operator may beinstructed to select mold members for the mold assembly. The moldmembers may be coded such that the controller may indicate to theoperator which molds to select by transmitting the code for each moldmember. The controller may also determine the type of gasket required toproperly seal the mold members together. Like the mold members, thegaskets may also be coded to make the selection of the appropriategasket easier.

The lens forming compositions may also be coded. For the production ofcertain kinds of lenses a specific lens forming composition may berequired. The controller may be configured to determine the specificcomposition required and transmit the code for that composition to theoperator. The controller may also signal to the operator when certainoperations need to be performed or when a particular operation iscompleted (e.g., when to place the mold assembly in the lens curingunit, when to remove the mold assembly, when to transfer the moldassembly, etc.).

Referring now to FIG. 38, another embodiment of a plastic lens curingapparatus is generally indicated by reference numeral 1000. As shown inFIG. 38, lens forming apparatus 1000 includes at least one coating unit1020, a pair of stacked lens curing units 1030 and 1035, a post-cureunit 1040, and a controller 1050. Preferably, apparatus 1000 includestwo coating units 1020. Coating unit 1020 is preferably configured toapply a coating layer to a mold member or a lens. Preferably, coatingunit 1020 is a spin coating unit. Each of the lens curing units, 1030and 1035, includes an activating light source for producing activatinglight. The activating light source is preferably configured to directlight toward a mold assembly. Post-cure unit 1040 is preferablyconfigured to complete the polymerization of partially cured plasticlenses. Post-cure unit 1040 preferably includes an activating lightsource and a heat source. Controller 1050 is preferably a programmablelogic controller. Controller 1050 is preferably coupled to coating units1020, lens curing units 1030 and 1035, and post-cure unit 1040, suchthat the controller may be capable of substantially simultaneouslyoperating the four units 1020, 1030, 1035 and 1040. Controller 50 may bea computer. During the production of plastic lenses the lens curing stepmay be the most time consuming part of the process. By adding additionalcuring units to the system the throughput of the system may beincreased, allowing the operator to form more lenses in a given timeperiod.

LENS FORMING COMPOSITIONS

The lens forming material may include any suitable liquid monomer ormonomer mixture and any suitable photosensitive initiator. As usedherein “monomer” is taken to mean any compound capable of undergoing apolymerization reaction. Monomers may include non-polymerized materialor partially polymerized material. When partially polymerized materialis used as a monomer, the partially polymerized material preferablycontains functional groups capable of undergoing further reaction toform a new polymer. The lens forming material preferably includes aphotoinitiator that interacts with activating light. In one embodiment,the photoinitiator absorbs ultraviolet light having a wavelength in therange of 300 to 400 nm. In another embodiment, the photoinitiatorabsorbs actinic light having a wavelength in the range of about 380 nmto 490 nm. The liquid lens forming material is preferably filtered forquality control and placed in the lens molding cavity 382 by pulling theannular gasket 380 away from one of the opposed mold members 378 andinjecting the liquid lens forming material into the lens molding cavity382 (See FIG. 11). Once the lens molding cavity 382 is filled with suchmaterial, the annular gasket 380 is preferably replaced into its sealingrelation with the opposed mold members 378.

Those skilled in the art will recognize that once the cured lens isremoved from the lens molding cavity 382 by disassembling the opposedmold members 378, the lens may be further processed in a conventionalmanner, such as by grinding its peripheral edge.

A polymerizable lens forming composition includes an aromatic-containingbis(allyl carbonate)-functional monomer and at least onepolyethylenic-functional monomer containing two ethylenicallyunsaturated groups selected from acrylyl or methacrylyl. In a preferredembodiment, the composition further includes a suitable photoinitiator.In other preferred embodiments, the composition may include one or morepolyethylenic-functional monomers containing three ethylenicallyunsaturated groups selected from acrylyl or methacrylyl, and a dye.

Aromatic-containing bis(allyl carbonate)-functional monomers includebis(allyl carbonates) of dihydroxy aromatic-containing material. Thedihydroxy aromatic-containing material from which the monomer is derivedmay be one or more dihydroxy aromatic-containing compounds. Preferablythe hydroxyl groups are attached directly to nuclear aromatic carbonatoms of the dihydroxy aromatic-containing compounds. The monomers arethemselves known and may be prepared by procedures well known in theart.

The aromatic-containing bis(allyl carbonate)-functional monomers may berepresented by the formula:

in which A₁ is the divalent radical derived from the dihydroxyaromatic-containing material and each R₀ is independently hydrogen,halo, or a C₁-C₄ alkyl group. The alkyl group is usually methyl orethyl. Examples of R₀ include hydrogen, chloro, bromo, fluoro, methyl,ethyl, n-propyl, isopropyl and n-butyl. Most commonly R₀ is hydrogen ormethyl; hydrogen is preferred. A subclass of the divalent radical A₁which is of particular usefulness is represented by the formula:

in which each R₁ is independently alkyl containing from 1 to about 4carbon atoms, phenyl, or halo; the average value of each (a) isindependently in the range of from 0 to 4; each Q is independently oxy,sulfonyl, alkanediyl having from 2 to about 4 carbon atoms, oralkylidene having from 1 to about 4 carbon atoms; and the average valueof n is in the range of from 0 to about 3. Preferably Q ismethylethylidene, viz., isopropylidene.

Preferably the value of n is zero, in which case A₁ is represented bythe formula:

in which each R₁, each a, and Q are as discussed in respect of FormulaII. Preferably the two free bonds are both in the ortho or parapositions. The para positions are especially preferred.

The dihydroxy aromatic-containing compounds from which A₁ is derived mayalso be polyether-functional chain extended compounds. Examples of suchcompounds include alkaline oxide extended bisphenols. Typically thealkaline oxide employed is ethylene oxide, propylene oxide, or mixturesthereof. By way of exemplification, when para, para-bisphenols are chainextended with ethylene oxide, the bivalent radical A₁ may often berepresented by the formula:

where each R₁, each a, and Q are as discussed in respect of Formula II,and the average values of j and k are each independently in the range offrom about 1 to about 4.

A preferred aromatic-containing bis(allyl carbonate)-functional monomeris represented by the formula:

and is commonly known as bisphenol A bis(allyl carbonate).

A wide variety of compounds may be used as the polyethylenic functionalmonomer containing two or three ethylenically unsaturated groups. Apreferred polyethylenic functional compound containing two or threeethylenically unsaturated groups may be generally described as theacrylic acid esters and the methacrylic acid esters of aliphaticpolyhydric alcohols, such as, for example, the di- and triacrylates andthe di- and trimethacrylates of ethylene glycol, triethylene glycol,tetraethylene glycol, tetramethylene glycol, glycerol, diethyleneglycol,butyleneglycol, propyleneglycol, pentanediol, hexanediol,trimethylolpropane, and tripropyleneglycol. Examples of specificsuitable polyethylenic—functional monomers containing two or threeethylenically unsaturated groups include trimethylolpropanetriacrylate(TMPTA), tetraethylene glycol diacrylate (TTEGDA), tripropylene glycoldiacrylate (TRPGDA), 1,6 hexanedioldimethacrylate (HDDMA), andhexanedioldiacrylate (HDDA).

In general, a photoinitiator for initiating the polymerization of thelens forming composition preferably exhibits an absorption spectrum overthe 300-400 nm range. High absorptivity of a photoinitiator in thisrange, however, is not desirable, especially when casting a thick lens.The following are examples of illustrative photoinitiator compounds:methyl benzoylformate, 2-hydroxy-2-methyl-1-phenylpropan-1-one,1-hydroxycyclohexyl phenyl ketone, 2,2-di-sec- butoxyacetophenone,2,2-diethoxyacetophenone, 2,2-diethoxy-2-phenyl-acetophenone,2,2-dimethoxy-2-phenyl-acetophenone, benzoin methyl ether, benzoinisobutyl ether, benzoin, benzil, benzyl disulfide,2,4-dihydroxybenzophenone, benzylideneacetophenone, benzophenone andacetophenone. Preferred photoinitiator compounds are 1-hydroxycyclohexylphenyl ketone (which is commercially available from Ciba-Geigy asIrgacure 184), methyl benzoylformate (which is commercially availablefrom Polysciences, Inc.), or mixtures thereof.

Methyl benzoylformate is a generally preferred photoinitiator because ittends to provide a slower rate of polymerization. The slower rate ofpolymerization tends to prevent excessive heat buildup (and resultantcracking of the lens) during polymerization. In addition, it isrelatively easy to mix liquid methyl benzoylformate (which is liquid atambient temperatures) with many acrylates, diacrylates, and allylcarbonate compounds to form a lens forming composition. The lensesproduced with the methyl benzoylformate photoinitiator tend to exhibitmore favorable stress patterns and uniformity.

A strongly absorbing photoinitiator will absorb most of the incidentlight in the first millimeter of lens thickness, causing rapidpolymerization in that region. The remaining light will produce a muchlower rate of polymerization below this depth and will result in a lensthat has visible distortions. An ideal photoinitiator will exhibit highactivity, but will have a lower extinction coefficient in the usefulrange. A lower extinction coefficient of photoinitiators at longerwavelengths tends to allow the activating light to penetrate deeper intothe reaction system. This deeper penetration of the activating lightallows photoinitiator radicals to form uniformly throughout the sampleand provide excellent overall cure. Since the sample may be irradiatedfrom both top and bottom, a system in which appreciable activating lightreaches the center of the thickest portion of the lens is preferred. Thephotoinitiator solubility and compatibility with the monomer system isalso an important requirement.

An additional consideration is the effect of the photoinitiatorfragments in the finished polymer. Some photoinitiators generatefragments that impart a yellow color to the finished lens. Although suchlenses actually absorb very little visible light, they may becosmetically undesirable.

Photoinitiators are often very system specific so that photoinitiatorsthat are efficient in one system may function poorly in another. Inaddition, the initiator concentration, to a large extent, may bedependent on the incident light intensity and the monomer composition.The identity of the initiator and its concentration may be important forany particular formulation. A concentration of initiator that is toohigh may lead to cracking and yellowing of the lens. Concentrations ofinitiator that are too low may lead to incomplete polymerization and asoft material.

Dyes and/or pigments are optional materials that may be present whenhigh transmission of light is not necessary.

The listing of optional ingredients discussed above is by no meansexhaustive. These and other ingredients may be employed in theircustomary amounts for their customary purposes so long as they do notseriously interfere with good polymer formulating practice.

1. Activating Light Curable Lens Forming Compositions

According to a preferred embodiment, a lens forming composition that maybe cured with activating light includes an aromatic-containing bis(allylcarbonate) functional monomer, preferably bisphenol A bis(allylcarbonate), admixed with one or more faster reacting polyethylenicfunctional monomers containing two acrylate or methacrylate groups suchas 1,6 hexanediol dimethacrylate (HDDMA), 1,6 hexanediol diacrylate(HDDA), tetraethylene glycol diacrylate (TTEGDA), and tripropyleneglycol diacrylate (TRPGDA) and optionally a polyethylenic functionalmonomer containing three acrylate groups such as trimethylolpropanetriacrylate (TMPTA). Generally, compounds containing acrylate groupspolymerize much faster than those containing allyl groups.

According to one embodiment, the liquid lens forming compositionincludes bisphenol A bis(allyl carbonate) in place of DEG-BAC. Thebisphenol A bis(allyl-carbonate) monomer has a higher refractive indexthan DEG-BAC making it more suitable for the production of thinnerlenses, which may be important with relatively thick positive ornegative lenses. The bisphenol A bis(allyl-carbonate) monomer iscommercially available from PPG Industries under the trade name HIM I orCR-73. Lenses made from this product sometimes have a very slight,barely detectable, degree of yellowing. A small amount of a blue dyeconsisting of 9, 10-anthracenedione, 1-hydroxy-4-[(4-methylphenyl)amino]available as Thermoplast Blue 684 from BASF Wyandotte Corp. ispreferably added to the composition to counteract the yellowing. Inaddition, the yellowing tends to disappear if the lens is subjected tothe above-described post-cure heat treatment. Moreover, if notpost-cured the yellowing tends to disappear at ambient temperature afterapproximately 2 months.

TTEGDA, available from Sartomer and Radcure, is a diacrylate monomerthat, preferably, is included in the composition because it is a fastpolymerizing monomer that reduces yellowing and yields a very clearproduct. If too much TTEGDA is included in the more preferredcomposition, i.e., greater than about 25% by weight, however, thefinished lens may be prone to cracking and may be too flexible as thismaterial softens at temperatures above 40° C. If TTEGDA is excludedaltogether, the finished lens may be too brittle.

HDDMA, available from Sartomer, is a dimethacrylate monomer that has avery stiff backbone between the two methacrylate groups. HDDMA,preferably, is included in the composition because it yields a stifferpolymer and increases the hardness and strength of the finished lens.This material is quite compatible with the bisphenol A bis(allylcarbonate) monomer. HDDMA contributes to high temperature stiffness,polymer clarity and speed of polymerization.

TRPGDA, available from Sartomer and Radcure, is a diacrylate monomerthat, preferably, is included in the composition because it providesgood strength and hardness without adding brittleness to the finishedlens. This material is also stiffer than TTEGDA.

TMPTA, available from Sartomer and Radcure, is a triacrylate monomerthat, preferably, is included in the composition because it providesmore crosslinking in the finished lens than the difunctional monomers.TMPTA has a shorter backbone than TTEGDA and increases the hightemperature stiffness and hardness of the finished lens. Moreover, thismaterial contributes to the prevention of optical distortions in thefinished lens. TMPTA also contributes to high shrinkage duringpolymerization. The inclusion of too much of this material in the morepreferred composition may make the finished lens too brittle.

Certain of the monomers that are preferably utilized, such as TTEGDA,TRPGDA and TNPTA, include impurities and have a yellow color in certainof their commercially available forms. The yellow color of thesemonomers is preferably reduced or removed by passing them through acolumn of alumina (basic) which includes aluminum oxide powder—basic.After passage through the alumina column differences between monomersobtained from different sources may be substantially eliminated. It ispreferred, however, that the monomers be obtained from a source whichprovides the monomers with the least amount of impurities containedtherein. The composition is preferably filtered prior to polymerizationthereof to remove suspended particles.

2. Lens Forming Compositions Including Ultraviolet/Visible LightAbsorbing Materials

Materials that absorb various degrees of ultraviolet/visible light maybe used in an eyeglass lens to inhibit ultraviolet/visible light frombeing transmitted through the eyeglass lens. The phrase“ultraviolet/visible light” is taken to mean light having a wavelengthin the ultraviolet light range or both the ultraviolet and visible lightranges. The phrase “ultraviolet/visible light absorbing compounds”refers to compounds which absorb ultraviolet/visible light. An eyeglasslens that includes ultraviolet/visible light absorbing compoundsadvantageously inhibits ultraviolet/visible light from being transmittedto the eye of a user wearing the lens. Thus, eyeglass lenses containingultraviolet/visible light absorbing compounds may function to protectthe eyes of a person from damaging ultraviolet/visible light.Photochromic pigments are one type of ultraviolet/visible lightabsorbing compounds. Photochromic inorganic lenses which contain silverhalide particles or cuprous halide particles suspended throughout thebody of the lens are well known and have been commercially available fordecades. Such inorganic lenses, however, suffer the disadvantage ofbeing relatively heavy and less comfortable to the wearer when comparedto organic lenses. Consequently, the majority of the eyeglass lensesproduced today are typically formed from organic materials rather thaninorganic materials. Accordingly, photochromic plastic eyeglass lenseshave been the subject of considerable attention in recent years.

Efforts to provide a plastic eyeglass lens which demonstratesphotochromic performance have primarily centered around permeatingand/or covering the surface(s) of an already formed lens withphotochromic pigments. This general technique may be accomplished by anumber of specific methods. For example, (a) the lens may be soaked in aheated bath which contains photochromic pigments, (b) photochromicpigments may be transferred into the surface of a plastic lens via asolvent assisted transfer process, or (c) a coating containingphotochromic pigments may be applied to the surface of a lens. A problemwith such methods may be that the lens often might not absorb enough ofthe photochromic pigments at low temperatures, resulting in an eyeglasslens which does not exhibit acceptable photochromic performance.Unfortunately, increasing the temperature used during absorption of thephotochromic pigments may not be a solution to this problem since athigh temperatures degradation of the polymer contained within the lensmay occur.

Attempts have also been made to incorporate photochromic pigments intothe liquid monomer from which plastic lenses are thermally polymerized.See U.S. Pat. No. 4,913,544 to Rickwood et al., wherein it is disclosedthat triethyleneglycol dimethacrylate monomer was combined with 0.2% byweight of various spiro-oxazine compounds and 0.1% benzoyl peroxide andsubsequently thermally polymerized to form non-prescription eyeglasslenses. Generally, efforts to incorporate photochromic pigments into theliquid monomer from which the lenses are polymerized have beenunsuccessful. It is believed that the organic peroxide catalystsutilized to initiate the thermal polymerization reaction tend to damagethe photochromic pigments, impairing their photochromic response.

Curing of an eyeglass lens using activating light to initiate thepolymerization of a lens forming composition generally requires that thecomposition exhibit a high degree of activating light transmissibilityso that the activating radiation may penetrate to the deeper regions ofthe lens cavity. Otherwise the resulting cast lens may possess opticalaberrations and distortions. The cast lens may also contain layers ofcured material in the regions closest to the transparent mold faces,sandwiching inner layers which are either incompletely cured, gelled,barely gelled, or even liquid. Often, when even small amounts ofultraviolet/visible light absorbing compounds of the types well known inthe art are added to a normally light curable lens forming composition,substantially the entire amount of lens forming composition containedwithin the lens cavity may remain liquid in the presence of activatinglight.

Photochromic pigments which have utility for photochromic eyeglasslenses absorb ultraviolet light strongly and change from an unactivatedstate to an activated state when exposed to ultraviolet light. Thepresence of photochromic pigments, as well as other ultraviolet/visiblelight absorbing compounds within a lens forming composition, generallydoes not permit enough activating radiation to penetrate into the depthsof the lens cavity sufficient to cause photoinitiators to break down andinitiate polymerization of the lens forming composition. Thus, it may bedifficult to cure a lens forming composition containingultraviolet/visible light absorbing compounds using activating light(e.g., if the activating light has a wavelength in the ultraviolet orvisible region). It is therefore desirable to provide a method for usingactivating light to initiate polymerization of an eyeglass lens formingmonomer which contains ultraviolet/visible light absorbing compounds, inspite of the high activating light absorption characteristics of theultraviolet/visible light absorbing compounds. Examples of suchultraviolet/visible light absorbing compounds other than photochromicpigments are fixed dyes and colorless additives.

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer, an ultraviolet/visible lightabsorbing compound, a photoinitiator, and a co-initiator. Herein, an“ophthalmic eyeglass lens” is taken to mean any plastic eyeglass lens,including a prescription lens, a non-prescription lens, a progressivelens, a sunglass lens, and a bifocal lens. The lens forming composition,in liquid form, is preferably placed in a mold cavity defined by a firstmold member and a second mold member. It is believed that activatinglight which is directed toward the mold members to activate thephotoinitiator causes the photoinitiator to form a polymer chainradical. The polymer chain radical preferably reacts with theco-initiator more readily than with the monomer. The co-initiator mayreact with a fragment or an active species of either the photoinitiatoror the polymer chain radical to produce a monomer initiating species inthe regions of the lens cavity where the level of activating light maybe either relatively low or not present.

Preferably, the monomers selected as components of the lens formingcomposition are capable of dissolving the ultraviolet/visible lightabsorbing compounds added to them. Herein, “dissolving” is taken to meanbeing substantially homogeneously mixed with. For example, monomers maybe selected from a group including polyether (allyl carbonate) monomers,multi-functional acrylate monomers, and multi-functional methacrylicmonomers for use in an ultraviolet/visible light absorbing lens formingcomposition.

In an embodiment, the following mixture of monomers, hereinafterreferred to as PRO-629, may be blended together before addition of othercomponents required to make the lens forming composition. This blend ofmonomers is preferably used as the basis for a lens forming compositionto which ultraviolet/visible light absorbing compounds are added.

32% Tripropyleneglycol diacrylate (SR-306)

21% Tetraethyleneglycol diacrylate (SR-268)

20% Trimethylolpropane triacrylate (SR-351)

17% Bisphenol A bis allyl carbonate (HiRi)

10% Hexanediol dimethacrylate (SR-239)

The acrylic and methacrylic monomers listed above are commerciallyavailable from Sartomer Company in Exton, Pa. The bisphenol A bis allylcarbonate is commercially available from PPG in Pittsburgh, Pa. Thehexanediol dimethacrylate is hereinafter referred to as HDDMA.

A polymerization inhibitor may be added to the monomer mixture atrelatively low levels to inhibit polymerization of the monomer atinappropriate times (e.g., during storage). Preferably about 0 to 50 ppmof monomethylether hydroquinone (MEHQ) are added to the monomer mixture.It is also preferred that the acidity of the monomer mixture be as lowas possible. Preferably less than about 100 ppm residual acrylic acidexists in the mixture. It is also preferred that the water content ofthe monomer mixture be relatively low, preferably less than about 0.15%.

Photoinitiators include: 1-hydroxycyclohexylphenyl ketone commerciallyavailable from Ciba Additives under the trade name of Irgacure 184;mixtures of bis(2,6-dimethoxybenzoyl) (2,4,4-trimethyl phenyl) phosphineoxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one commerciallyavailable from Ciba Additives under the trade name of Irgacure 1700;mixtures of bis(2,6-dimethoxybenzoyl) (2,4,4 trimethyl phenyl) phosphineoxide and 1-hydroxycyclohexylphenyl ketone commercially available fromCiba Additives under the trade names of Irgacure 1800 and Irgacure 1850;2,2-dimethoxy-2-phenyl acetophenone commercially available from CibaAdditives under the trade name of Irgacure 651;2-hydroxy-2-methyl-1-phenyl-propan-1-one commercially available fromCiba Additives under the trade names of Darocur 1173; mixtures of2,4,6-trimethylbenzoyl-diphenylphoshine oxide and2-hydroxy-2-methyl-1-phenyl-propan-1-one commercially available fromCiba Additives under the trade name of Darocur 4265;2,2-diethoxyacetophenone (DEAP) commercially available from FirstChemical Corporation of Pascagoula, Miss., benzil dimethyl ketalcommercially available from Sartomer Company under the trade name ofKB-1; an alpha hydroxy ketone initiator commercially available fromSartomer company under the trade name of Esacure KIP100F; 2-methylthioxanthone (MTX), 2-chloro-thioxanthone (CTX), thioxanthone (TX), andxanthone, all commercially available from Aldrich Chemical;2-isopropyl-thioxanthone (ITX) commercially available from AcetoChemical in Flushing, N.Y.; mixtures of triaryl sulfoniumhexafluoroantimonate and propylene carbonate commercially available fromSartomer Company under the trade names of SarCat CD 1010, SarCat 1011,and SarCat K185; diaryliodinium hexafluoroantimonate commerciallyavailable from Sartomer Company under the trade name of SarCat CD-1012;mixtures of benzophenone and 1-hydroxycyclohexylphenyl ketonecommercially available from Ciba Additives under the trade name ofIrgacure 500;2-benzyl-2-N,N-dimethylamino-1-(4-morpholinophenyl)-1-butanonecommercially available from Ciba Additives under the trade name ofIrgacure 369;2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one commerciallyavailable from Ciba Additives under the trade name of Irgacure 907;bis(η5-2,4-cyclopentadien-1-yl)-bis-[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl] titanium commercially available from Ciba Additives under thetrade name of Irgacure 784 DC; mixtures of 2,4,6-trimethyl-benzophenoneand 4-methyl-benzophenone commercially available from Sartomer Companyunder the trade name of EsaCure TZT; and benzoyl peroxide and methylbenzoyl formate both available from Aldrich Chemical in Milwaukee, Wis.

A preferred photoinitiator is bis(2,6-dimethoxybenzoyl) (2,4,4 trimethylphenyl) phosphine oxide, commercially available from Ciba Additives inTarrytown, N.Y. under the trade name of CGI-819. The amount of CGI-819present in a lens forming composition containing photochromic compoundspreferably ranges from about 30 ppm by weight to about 2000 ppm byweight.

Co-initiators include reactive amine co-initiators commerciallyavailable from Sartomer Company under the trade names of CN-381, CN-383,CN-384, and CN-386, where these co-initiators are monoacrylic amines,diacrylic amines, or mixtures thereof. Other co-initiators includeN-methyldiethanolamine (NMDEA), triethanolamine (TEA),ethyl-4-dimethylaminobenzoate (E-4-DMAB), ethyl-2-dimethylaminobenzoate(E-2-DMAB), all commercially available from Aldrich Chemicals.Co-initiators which may also be used includen-butoxyethyl-4-dimethylamino benzoate, p-dimethyl amino benzaldehyde.Other co-initiators include N, N-dimethyl-p-toluidine,octyl-p-(dimethylamino) benzoate commercially available from The FirstChemical Group of Pascagoula, Miss.

Preferably, the co-initiator is N-methyldiethanolamine (NMDEA)commercially available from Aldrich Chemical in Milwaukee, Wis., CN-384commercially available from Sartomer Company, or CN-386 alsocommercially available from Sartomer Company. The quantity of NMDEApresent in a lens forming composition containing photochromic pigmentsis preferably between about 1 ppm by weight and 7% by weight and morepreferably between about 0.3% and 2% by weight. Further, certain fixedpigments which may be added to the lens forming composition to create abackground color within the lens (i.e., to tint the lens), may alsofunction as co-initiators. Examples of such fixed pigments includeThermoplast Blue P, Oil Soluble Blue II, Thermoplast Red 454,Thermoplast Yellow 104, Zapon Brown 286, Zapon Brown 287, allcommercially available from BASF Corporation in Holland, Mich.

Ultraviolet/visible light absorbing compounds which may be added to anormally ultraviolet/visible light transmissible lens formingcomposition include 2-(2H benzotriazole-2-yl)-4-(1,1,3,3tetramethylbutyl)phenol and 2-hydroxy-4-methoxybenzophenone, bothcommercially available from Aldrich Chemical as well as mixtures of2-[4-((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazineand2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl-1,3,5-triazinecommercially available from Ciba Additives under the trade name ofTinuvin 400, mixtures of poly (oxy-1,2-ethanediyl),α-(3-(3-(2H-benzotriazol-2-yl)-5-(1,1dimethylethyl)-4-hydroxyphenyl)-1-oxopropyl)-ω-hydroxyand poly (oxy-1,2-ethanediyl),α-(3-(3-(2H-benzotriazol-2-yl)-5-(1,1dimethylethyl)-4-hydroxyphenyl)-1-oxopropyl)-ω-(3-(3-(2H-benzotriazol-2-yl)-5-1,1-dimethylethyl)-4-hydroxyphenyl)-1-oxopropoxy)commercially available from Ciba Additives under the trade name ofTinuvin 1130. Other ultraviolet/visible light absorbers may includeTinuvin 328, Tinuvin 900, 2-(2 hydroxy-5-methyl-phenyl) benzotriazole,ethyl-2-cyano 3,3-diphenyl acrylate, and phenyl salicylate.

While any number of families of photochromic pigments may beincorporated into the blend of monomers, either individually or incombination, spiropyrans, spironaphthoxazines, spiropyridobenzoxazines,spirobenzoxazines, napthopyrans, benzopyrans, spirooxazines,spironapthopyrans, indolinospironapthoxazines,indolinospironapthopyrans, diarylnapthopyrans, and organometallicmaterials are of particular interest. A phenylmercury compound availablefrom Marks Polarized Corporation in Hauppauge, N.Y. under the trade nameof A241 may be an appropriate organometallic material. The quantity ofphotochromic pigments present in the lens forming composition ispreferably sufficient to provide observable photochromic effect. Theamount of photochromic pigments present in the lens forming compositionmay widely range from about 1 ppm by weight to 5% by weight. Inpreferred compositions, the photochromic pigments are present in rangesfrom about 30 ppm to 2000 ppm. In the more preferred compositions, thephotochromic pigments are present in ranges from about 150 ppm to 1000ppm. The concentration may be adjusted depending upon the thickness ofthe lens being produced to obtain optimal visible light absorptioncharacteristics.

In an embodiment, hindered amine light stabilizers may be added to thelens forming composition. It is believed that these materials act toreduce the rate of degradation of the cured polymer caused by exposureto ultraviolet light by deactivating harmful polymer radicals. Thesecompounds may be effective in terminating oxygen and carbon freeradicals, and thus interfering with the different stages ofauto-oxidation and photo-degradation. A useful hindered amine lightstabilizer is bis(1,2,2,6,6-pentamethyl-4-piperidinyl)-sebacatecommercially available from Ciba Additives under the trade name ofTinuvin 292. Hindered phenolic anti-oxidants and thermal stabilizers mayalso be added to a lens forming composition. The hindered phenoliccompounds hereof include thiodiethylenebis(3,5,-di-tert-butyl-4-hydroxy)hydroxycinnamate commercially availablefrom Ciba Additives under the trade name of Irganox 1035 andoctadecyl-3,5-bis(1,1-dimethylethyl)-4-hydroxybenzene-propanoatecommercially available from Ciba Additives under the trade name ofIrganox 1076.

Preferably, more than one monomer and more than one initiator are usedin a lens forming composition to ensure that the initial polymerizationof the lens forming composition with activating light does not occurover too short a period of time. The use of such a lens formingcomposition may allow greater control over the gel formation, resultingin better control of the optical quality of the lens. Further, greatercontrol over the rate of exothermic heat generation may be achieved.Thus, cracking of the lens and premature release of the lens from themold which are typically caused by the release of heat may be prevented.An example of a poor initiator system was observed when CGI-819 was usedalone as a photoinitiator in combination with the PRO-629 monomer blendto which ultraviolet/visible light absorbing compounds had been added.When such an initiator system was used, a fast rate of reaction occurrednear the surface of the lens cavity while a very slow rate of reactionoccurred in the deeper regions of the cavity. The resultant lensexhibited unwanted waves and distortions.

In another example, a small amount of a co-initiator, i.e., NMDEA wasadded to the above lens forming composition. During the curing process,two separate waves of heat were generated when the composition wasirradiated continuously with activating light at about 600microwatts/cm². One possible explanation for this phenomena is that thefirst wave resulted from reaction of the NMDEA and the second waveresulted from the reaction of the unconsumed portion of the CGI-819.Another possible explanation is that the rate of reaction was faster inthe top portion than in the bottom portion of the lens formingcomposition since activating light was separately directed toward boththe bottom and the top mold members. A third wave of heat generation mayalso occur if the rate of reaction at the middle portion of the lensforming composition is different from the rates at the bottom and topportions. Unfortunately, the resulting lens possessed waves anddistortions. It is postulated, however, that as the amounts of bothCGI-819 and NMDEA are increased, the two waves of exothermic heat willmove closer together in time, causing the optical quality of the lens toimprove, the hardness of the lens to increase, and the rate of heatgeneration to be slow enough to prevent cracking and premature releaseof the lens from the mold.

It is anticipated that the optimal amount of initiators may be achievedwhen the total amount of both initiators are minimized subject to theconstraint of complete polymerization and production of a rigid,aberration free lens. The relative proportions of the photoinitiator tothe co-initiator may be optimized by experimentation. For example, anultraviolet/visible light absorptive lens forming composition thatincludes a photoinitiator with no co-initiator may be cured. If wavesand distortions are observed in the resulting lens, a co-initiator maythen be added to the lens forming composition by increasing amountsuntil a lens having the best optical properties is formed. It isanticipated that excess co-initiator in the lens forming compositionshould be avoided to inhibit problems of too rapid polymerization,yellowing of the lens, and migration of residual, unreacted co-initiatorto the surface of the finished lens.

The following charts may be used as a guide in the selection of anappropriate photoinitiator/co-initiator system for variousultraviolet/visible light absorbing lens forming compositions.

Photoinitiator Guide Lens Forming Composition Type UV Absorptive UVAbsorptive UV Absorptive Photoinitiator Yellowness Odor Shelf LifePhotochromic Fixed Pigments Colorless CGI 819 Moderate Low Good GoodGood Good Irgacure 184 Low Low Good Good Good Good Irgacure 651 High LowPoor Less Preferred Good Less Preferred Irgacure 1700 High Low Fair GoodGood Less Preferred Irgacure 1800 Moderate Low Good Good Good LessPreferred Irgacure 1850 Moderate Low Good Good Good Good Darocur 1173High Low Good Good Good Less Preferred Darocur 4265 High Moderate FairGood Good Less Preferred DEAP High Strong Poor Less Preferred LessPreferred Less Preferred KB-1 High Strong Poor Less Preferred LessPreferred Less Preferred EsaCure KIP100F High Strong Poor Less PreferredLess Preferred Less Preferred Irgacure 369 High Moderate Poor LessPreferred Good Less Preferred Irgacure 500 High Strong Poor LessPreferred Less Preferred Less Preferred Irgacure 784 DC High Low PoorLess Preferred Less Preferred Less Preferred Irgacure 907 High StrongPoor Less Preferred Less Preferred Less Preferred Benzoyl peroxideModerate Low Poor Less Preferred Less Preferred Less Preferred Methylbenzoyl formate Moderate Low Fair Less Preferred Less Preferred LessPreferred EsaCure TZT High Low Poor Less Preferred Less Preferred LessPreferred ITX High Low Poor Less Preferred Good Good MTX High Low PoorLess Preferred Good Good CTX High Low Poor Less Preferred Less PreferredLess Preferred TX High Low Poor Less Preferred Less Preferred LessPreferred Xanthone High Low Poor Less Preferred Less Preferred LessPreferred CD-1010 Low Low Poor Good Less Preferred Less PreferredCD-1011 Low Low Poor Good Less Preferred Less Preferred CD1012 Low LowPoor Good Good Good Co-initiator Guide Lens Forming Composition TypeCo-initiator UV Absorptive Photochromic UV Absorptive Fixed Pigments UVAbsorptive Colorless CN-383 Good CN-384 Good Good Good CN-386 Good GoodGood NMDEA Good Good Good N,NMDEA Less Preferred Less Preferred TEA LessPreferred Less Preferred E-4-DMAB Good Less Preferred Less PreferredE-2-DMAB Less Preferred Less Preferred

As mentioned above, exothermic reactions occur during the curing processof the lens forming composition. The thicker portions of the lensforming composition may generate more heat than the thinner portions ofthe composition as a result of the exothermic reactions taking place. Itis believed that the speed of reaction in the thicker sections is slowerthan in the thinner sections. Thus, in a positive lens a “donut effect”may occur in which the relatively thin outer portion of the lens formingcomposition reaches its fully cured state before the relatively thickinner portion of the lens forming composition. Conversely, in a negativelens the relatively thin inner portion of the lens forming compositionmay reach its fully cured state before the relatively thick outerportion of the lens forming composition.

An eyeglass lens formed using the above described lens formingcomposition may be applicable for use as a prescription lens or for anon-prescription lens. Particularly, such a lens may be used insunglasses. Advantageously, photochromic sunglass lenses would remainlight enough in color to allow a user to see through them clearly whileat the same time prohibiting ultraviolet light from passing through thelenses. In one embodiment, a background dye may be added to thephotochromic lens to make the lens appear to be a dark shade of color atall times like typical sunglasses.

3. Variable Color Photochromic Lens Forming Compositions

Photochromic compounds tend to absorb certain wavelengths of lightstrongly and change from a colorless state to a colored state. The“colorless state” of a photochromic compound is defined as the state inwhich the compound exhibits no color or only a slight amount of color.The “colored state” of a photochromic compound is defined as the statein which the photochromic compound exhibits a visible light colorsignificantly stronger than the colorless state. A “photochromicactivating light source” is defined as any light source that produceslight having a wavelength which causes a photochromic compound to changefrom a colorless state to a colored state. “Photochromic activatinglight” is defined as light having a wavelength capable of causing aphotochromic compound to change from a colorless state to a coloredstate. Photochromic activating light typically includes light having awavelength from between about 200 nm to about 500 nm. A photochromicactivating light source may also produce other wavelengths of light,besides photochromic activating light.

A photochromic compound which is transparent and normally colorlesswill, upon exposure to a photochromic activating light source (e.g.,ultraviolet light), become colored and, therefore, less visible lighttransmissive. When removed from the photochromic activating lightsource, the photochromic substance tends to revert back to its colorlessstate. This may be represented by the following equation:

The colorless form is believed to be in equilibrium with the coloredform. The equilibrium between the colorless form and the colored formmay be controlled by the presence of photochromic activating light(represented by hv). If a photochromic compound is exposed to aphotochromic activating light source, the equilibrium tends to shifttoward the colored form of the photochromic compound. When thephotochromic activating light source is removed, or reduced, or if thephotochromic compound is heated, the equilibrium tends to shift backtoward the colorless form of the photochromic compound. Photochromiccompounds of this type may be particularly useful in eyeglass lenses. Inthe absence of photochromic activating light (e.g., when indoors) theglasses tend to remain colorless and light transmissive. When exposed toa photochromic activating light source (e.g., sunlight) the photochromiccompounds become activated and colored, lowering the light transmittanceof the lens. The term “activated color” is defined as the color which aneyeglass attains when photochromic compounds, which are included in theeyeglass lens, become activated and colored when exposed to aphotochromic activating light source. In this manner, photochromiccompounds may allow a single lens to be used as both an indoor lens andan outdoor lens.

When incorporated into transparent plastic lenses and activated byexposure to a photochromic activating light source, photochromiccompounds tend to exhibit variety of colors (e.g., red, orange, yellow,green, blue, indigo, purple, violet, gray, and brown), causing the lensthat the photochromic compounds are disposed within to exhibit the colorof the photochromic compound. Thus, the activated color of aphotochromic eyeglass lens may be controlled by the particularphotochromic compounds dispersed within the eyeglass lens.

It is known that the activated color of a photochromic eyeglass lens maytake on more neutral colors, such as brown or gray, by forming theeyeglass lens with two or more photochromic compounds present. U.S. Pat.No. 4,968,454 to Crano et. al., describes a composition which includestwo photochromic compounds used to form plastic lenses. The formedplastic lenses exhibit a gray or brown color in the presence of aphotochromic activating light source. Crano et. al., describes the useof two or more organic photochromic compounds within a plastic lens. Oneof the organic photochromic compounds exhibits an absorption maximum inthe range between about 590 nm to about 700 nm in the presence of aphotochromic activating light source. The other organic photochromiccompound exhibits an absorption maximum in the range between about 400nm and less than about 500 nm. The ratios of the compounds may be variedto produce lenses which exhibit a variety of activated colors.Typically, either the ratios of the photochromic compounds or thespecific photochromic compound used may be varied to effect a change inthe activated color of the lens.

In an embodiment, a composition which includes two or more photochromiccompounds may further include a light effector composition to produce alens which exhibits an activated color which differs from an activatedcolor produced by the photochromic compounds without the light effectorcomposition. The light effector composition may include any compoundwhich absorbs photochromic activating light. Light effector compositionsmay include photoinitiators, non-photochromic ultraviolet/visible lightabsorbers (as defined above), non-photochromic dyes, and ultravioletlight stabilizers. In this manner, the activated color of a lens may bealtered without altering the ratio and or composition of thephotochromic compounds. This may be particularly important when largebatches of lens forming compositions are prepared before use. Ifphotochromic lenses which exhibit a variety of activated colors are tobe produced, it is typically necessary to create a separate lens formingcomposition for each colored lens. By using a light effectorcomposition, a single lens forming composition may be used as a basesolution to which a light effector may be added in order to alter theactivated color of the formed lens.

The activated color of a photochromic lens may be determined by thevisible light absorption of the photochromic compounds in their coloredstate. When two photochromic compounds are present, the equilibriumbetween the colored and the colorless forms may be represented by thefollowing equations:

Where PC¹ Colorless represents the colorless form of the firstphotochromic compound; PC² Colorless represents the colorless form ofthe second photochromic compound; PC light¹ represents the wavelengthsof light which cause PC¹ Colorless to shift its colored state (PC¹Colored); PC light² represents the wavelengths of light which cause PC¹Colorless to shift to its colored state (PC² Colored). As depicted inFIG. 37, the wavelength of light which may activate the photochromiccompounds PC¹ and PC² may differ depending on the chemical structure ofthe photochromic compounds. PC light¹, which activates the firstphotochromic compound PC¹, has a wavelength in the range between aboutλ¹ and λ² nm. PC light², which activates the second photochromiccompound, has a wavelength in the range between about λ³ and λ⁴ nm.These wavelength ranges may differ (as depicted in FIG. 37) or may besubstantially the same.

The addition of a light effector composition which absorbs photochromicactivating light may cause a change in the activated color of the formedlens. The change in activated color may be dependent on the range ofphotochromic activating light absorbed by the light effectorcomposition. The addition of light effector compositions may havedifferent effects on the activated color of the lens, depending on theabsorbance of the light effector composition. In one embodiment, thelight effector composition may interfere with the photochromic activityof the first photochromic compound (PC¹). As illustrated in theequations below, the presence of a light effector composition(Effector¹) may cause a shift in the equilibrium of PC¹ while havinglittle or no effect on PC².

Such an effect may cause an increase or decrease in the concentration ofPC¹ Colored produced when the lens is exposed to a photochromicactivating light source. The equilibrium of the other photochromiccompound PC² may not be significantly altered. Thus, the activated colorof the lens may be significantly different than the activated color of alens that does not include a light effector composition (Effector¹). Inthe above case, if the concentration of PC¹ Colored is, for example,decreased, the activated color of the lens may become shifted toward theactivated color of PC². For example, if the activated color of a lenswhich includes PC¹ only is blue-green; with PC² only is red; and withboth PC¹ and PC² is gray; the activated color of the lens may becomemore red (e.g., shift from gray to green, yellow, orange or red) if theconcentration of PC¹ Colored is decreased. It is theorized that such aneffector may have an absorbance in a region of light similar to the PCLight¹ region. The effector may interfere with the absorption ofphotochromic activating light by PC¹ by competing with PC¹ for thelight. PC² remains relatively unaffected by the light effectorcomposition since its active photochromic activating light range differssignificantly from the photochromic activating light range for PC¹. Thisis graphically illustrated in FIG. 37, where Effector¹ is depicted ashaving an absorption within the PC¹ Light¹ region. By competing with PC¹for the photochromic activating light, Effector¹ may cause a decrease inthe amount of PC¹ Colored being produced.

In another embodiment, a light effector may interact with bothphotochromic compounds, altering the amount of PC¹ colored and PC²colored produced. The equation below depicts this case:

Such an effect may cause an increase or decrease in the concentration ofboth PC¹ Colored and PC² Colored produced when the lens is exposed to aphotochromic activating light source. This change in the equilibrium maycause the activated color of the lens to be significantly different thanthe activated color of a lens that does not include a light effectorcomposition. In the above case if the concentration of PC¹ Colored is,for example, decreased and the concentration of PC² Colored is, forexample, increased, the activated color of the lens may become shiftedtoward the activated color of PC² colored. For example, if the activatedcolor of a lens which includes PC¹ only is blue-green; with PC² only isred; and with both PC¹ and PC² is gray; the activated color of the lensmay become more red in the presence of the light effector composition.The direction of the shift may depend on which photochromic compound iseffected more by the presence of the light effector composition. It istheorized that the light effector composition (Effector²) may have anabsorbance in a region that significantly overlaps the PC Light¹ and PCLight² regions. The light effector composition interferes with theabsorption of photochromic activating light by both PC¹ and PC² bycompeting with the compounds for light having the appropriate activatingwavelength. If the light effector interferes with the photochromic lightabsorption of PC¹ to a greater extent then PC² the color may shifttoward PC². Alternatively, the activated color may shift toward PC¹ ifthe light effector absorption interferes with the absorption ofphotochromic light by PC² to a greater extent than PC¹. In FIG. 37,Effector² is depicted as having an absorption within both the PC¹ andPC² absorption region.

In another embodiment, a light effector composition may interfere withthe photochromic activity of the second photochromic compound (PC²). Asillustrated in the equations below, the presence of a light effectorcomposition (Effector³) may cause a shift in the equilibrium of PC²while having little or no effect on PC¹.

Such an effect may cause an increase or decrease in the concentration ofPC² Colored produced when the lens is exposed to a photochromicactivating light source. The equilibrium of the other photochromiccompound PC¹ may not be significantly altered. In the above case, if theconcentration of PC² Colored is, for example, decreased, the activatedcolor of the lens may become shifted toward the activated color of PC¹.For example, if the activated color of a lens which includes PC¹ only isblue-green; with PC² only is red; and with both PC¹ and PC² is gray; theactivated color of the lens may become more blue (e.g., shift from grayto green, green-blue, or blue) if the concentration of PC¹ Colored isdecreased. It is theorized that such an effector may have an absorbancein a region of light similar to the PC Light² region. The effector mayinterfere with the absorption of photochromic activating light by PC² bycompeting with PC² for the light. PC¹ remains relatively unaffected bythe light effector composition since its active photochromic activatinglight range differs significantly from the photochromic activating lightrange for PC². This is graphically illustrated in FIG. 37, whereEffector¹ is depicted as having an absorption within the PC Light²region. By competing with PC² for the photochromic activating light,Effector³ may cause a decrease in the amount of PC² Colored beingproduced.

While the above examples relate to the use of two photochromiccompounds, light effector compositions may be used to effect theactivated color of a lens which includes more than two photochromiccompounds. The color changes for these systems may be more varied thandescribed above, due to the variety of ranges in which the photochromiccompounds absorb the photochromic activating light. For example, ifthree photochromic compounds are present, with activated colors of red,blue and green, a variety of colors may be produced depending on theinteraction of the light effector composition with the photochromicactivating light. The light effector may absorb the photochromicactivating light such that the concentration of the colored form of twoof the three photochromic compounds is reduced. The formed lens wouldthan exhibit a color which is closest to the activated color of thenon-effected photochromic compound. In the above example, a lens with anactivated color of substantially blue, red, or green may be obtained bythe addition of a light effector. Alternatively, the light effectorcompound may reduce the concentration of the colored form of only one ofthe photochromic compounds. In the above example, the activated color ofthe lens may become yellow (from red and green, with reduced amount ofblue), green-blue (from green and blue, with reduced amount of red) orpurple (from red and blue, with reduced amount of green). A fullspectrum of activated colors may be produced by changing the compositionof the light effector composition, without having to alter the ratio orchemical composition of the photochromic compounds.

It should also be understood that the light effector composition mayinclude one or more light effector compounds. The use of multiple lighteffector compounds may allow the activated color of the lens to befurther altered.

In another embodiment, a photochromic activating light dye may be addedto the lens forming composition to alter the activated color of a lens.The dye preferably exhibits a dye color when exposed to visible light.The dye color, however, is not significantly altered in the presence orabsence of photochromic activating light. When mixed with a lens formingcomposition which includes at least one photochromic compound the dyemay alter the activated color of the lens, as well as the color of thelens in the absence of photochromic activating light.

In one embodiment, the dye may interfere with the photochromic activityof a photochromic compound. The activated color of a lens formed withoutthe dye would preferably change when the dye is added to the lens. Theactivated color of the lens may vary depending on the type of dyechosen. In one embodiment, the dye may interfere with the absorbance ofphotochromic activating light by the photochromic compound. Thisinterference may lead to a reduced concentration of the colored form ofthe photochromic compound. The activated color of the lens may be amixture of the dye color and the photochromic color. For example, if adye is blue and the photochromic compound is red, the lens may take on apurple color (i.e., a combination of the two colors).

It should be understood that the activated color of the lens may besignificantly different the an activated color of a lens in which thephotochromic compound is unaffected by the dye. When the absorption ofphotochromic activating light by the photochromic compound is unaffectedby the dye, the intensity of the colored form of the photochromiccompound may not be reduced. Thus, the activated color of the lens isformed from a mixture of the dye color and the full intensity of thecolored form of the photochromic compound. When the dye interferes withthe photochromic activating light absorbance of the photochromiccompound, the color of the lens is based on a combination of the dye andthe reduced intensity of the colored form of the photochromic compound.The reduced intensity of the colored form of the photochromic compoundmay cause the lens to have a color that is substantially different fromthe color produced when the unaffected colored form of the photochromiccompound is mixed with the dye.

While described above for one photochromic compound, it should beunderstood that the dye may have an effect on mixtures of photochromiccompounds such that a full spectrum of colors may be achieved. Theselection of the appropriate dye based on the photochromic compoundspresent allows the color of the lenses to be altered without changingthe ratio of the photochromic compounds.

In an embodiment, a lens forming composition includes at least twophotochromic compounds. The photochromic compounds are preferably chosento that have an activated color at opposite ends of the visible spectrum(e.g., blue and red). In one embodiment, the photochromic compounds maybe Reversacol Berry Red (giving a red activated color) and ReversacolSea Green (giving a blue-green color). The appropriate mixture of thesetwo photochromic compounds gives the formed lens an activated color ofgray. The addition of effectors may cause the formed lens to have a widevariety of activated colors (e.g. red, orange, yellow, yellow green,green, aqua-green, blue, violet, purple, or brown). These changes incolor may be accomplished without altering the ratio between the firstand second photochromic compounds.

A lens forming composition based on the PRO-629 mixture of monomers maybe used to develop photochromic lenses (See the section entitled “LensForming Compositions Including Ultraviolet/Visible Light AbsorbingMaterials”). The remainder of the lens forming composition preferablyincludes photoinitiators, co-initiators, photochromic compounds. Theamount of photochromic pigments present in the lens forming compositionmay widely range from about 1 ppm by weight to 5% by weight. Inpreferred compositions, the photochromic pigments are present in rangesfrom about 30 ppm to 2000 ppm. In the more preferred compositions, thephotochromic pigments are present in ranges from about 150 ppm to 1000ppm. The concentration may be adjusted depending upon the thickness ofthe lens being produced to obtain optimal visible light absorptioncharacteristics.

To alter the color of the active lens formed from this base compositiona light effector composition may be added to the base composition. Thelight effector composition preferably includes one or more lighteffectors. The light effector composition may be a pure composition ofone or more light effectors. Alternatively, the light effectors may bediluted in a solution which has a composition similar to the basecomposition. The light effectors preferably include photochromicactivating light absorbing compounds. More preferably, non-photochromicphotochromic activating light absorbing compounds are added to alter theactivated color of the formed lens. Examples of light effectors includepolymerization inhibitors (e.g., MEHQ), photoinitiators, co-initiators,fixed pigments and dyes, and hindered amine light stabilizers. All ofthese classes of compounds are described in greater detail in theprevious section. After the light effector composition has been added,the amount of light effectors present in the lens forming compositionmay widely range from about 1 ppm by weight to 5% by weight. Inpreferred compositions, the light effectors are present in ranges fromabout 30 ppm to 2000 ppm. In the more preferred compositions, the lighteffectors are present in ranges from about 150 ppm to 1000 ppm. Theconcentration may be adjusted depending upon the thickness of the lensbeing produced to obtain optimal visible light absorptioncharacteristics.

An advantage of the described composition is that the activated color ofa lens may be altered without altering the ratio and or composition ofthe photochromic compounds. By using a light effector composition, asingle lens forming composition may be used as a base composition towhich a light effector composition may be added in order to alter theactivated color of the formed lens. The base composition may be suppliedfor use in the production of a variety of photochromic lenses. Alongwith the base composition, a light effector composition, which includesone or more light effector compounds, may be included with the basecomposition. The light effector composition may be added to the basecomposition to alter the activated color of the formed lenses. In thismanner, a single stock photochromic lens forming composition may be usedto create photochromic lenses having a variety of activated colors.

In another embodiment, the base composition and at least two lighteffector compositions may be package together as a kit. The addition ofthe first light effector composition may alter the activated color ofthe formed lenses to produce a first color. The addition of the secondlight effector composition may alter the activated color of the formedlenses to produce a second color. Additional light effectorscompositions may also be included with the kit. The kit may allow a userto produce lens forming compositions which may be used to produce lenshaving a variety of activated colors by the addition of the appropriatelight effector composition to the base composition.

4. Mid-Index Lens Forming Composition

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer composition and aphotoinitiator composition.

The monomer composition preferably includes an aromatic containingpolyethylenic polyether functional monomer. In an embodiment, thepolyether employed is an ethylene oxide derived polyether, propyleneoxide derived polyether, or mixtures thereof. Preferably, the polyetheris an ethylene oxide derived polyether. The aromatic polyetherpolyethylenic functional monomer preferably has the general structure(V), depicted below where each R₂ is a polymerizable unsaturated group,m and n are independently 1 or 2, and the average values of j and k areeach independently in the range of from about 1 to about 20. Commonpolymerizable unsaturated groups include vinyl, allyl, allyl carbonate,methacrylyl, acrylyl, methacrylate, and acrylate.

R₂—[CH₂—(CH₂)_(m)—O]_(j)—A₁—[O—(CH₂)_(n)—CH₂]_(k)—R₂

A₁ is the divalent radical derived from a dihydroxy aromatic-containingmaterial. A subclass of the divalent radical A₁ which is of particularusefulness is represented by formula (II):

in which each R₁ is independently alkyl containing from 1 to about 4carbon atoms, phenyl, or halo; the average value of each (a) isindependently in the range of from 0 to 4; each Q is independently oxy,sulfonyl, alkanediyl having from 2 to about 4 carbon atoms, oralkylidene having from 1 to about 4 carbon atoms; and the average valueof n is in the range of from 0 to about 3. Preferably Q ismethylethylidene, viz., isopropylidene.

Preferably the value of n is zero, in which case A₁ is represented byformula (III):

in which each R₁, each a, and Q are as discussed with respect to FormulaII. Preferably the two free bonds are both in the ortho or parapositions. The para positions are especially preferred.

In an embodiment, when para, para-bisphenols are chain extended withethylene oxide, the central portion of the aromatic containingpolyethylenic polyether functional monomer may be represented by theformula:

where each R₁, each a, and Q are as discussed with respect to FormulaII, and the average values of j and k are each independently in therange of from about 1 to about 20.

In another embodiment, the polyethylenic functional monomer is anaromatic polyether polyethylenic functional monomer containing at leastone group selected from acrylyl or methacrylyl. Preferably the aromaticpolyether polyethylenic functional monomer containing at least one groupselected from acrylate and methacrylate has the general structure (VI),depicted below where R₀ is hydrogen or methyl, where each R₁, each a,and Q are as discussed with respect to Formula II, where the values of jand k are each independently in the range of from about 1 to about 20,and where R₂ is a polymerizable unsaturated group (e.g., vinyl, allyl,allyl carbonate, methacrylyl, acrylyl, methacrylate, or acrylate).

In one embodiment, the aromatic containing polyether polyethylenicfunctional monomer is preferably an ethoxylated bisphenol Adi(meth)acrylate. Ethoxylated bisphenol A di(meth)acrylates have thegeneral structure depicted below where each R₀ is independently hydrogenor methyl, each R₁, each a, and Q are as discussed with respect toFormula II, and the values of j and k are each independently in therange of from about 1 to about 20.

Preferred ethoxylated bisphenol A dimethacrylates include ethoxylated 2bisphenol A diacrylate (where j+k=2, and R₀ is H), ethoxylated 2bisphenol A dimethacrylate (where j+k=2, and R₀ is Me), ethoxylated 3bisphenol A diacrylate (where j+k=3, and R₀ is H), ethoxylated 4bisphenol A diacrylate (where j+k=4, and R₀ is H), ethoxylated 4bisphenol A dimethacrylate (where j+k=4, and R₀ is Me), ethoxylated 6bisphenol A dimethacrylate (where j+k=6, and R₀ is Me), ethoxylated 8bisphenol A dimethacrylate (where j+k=8, and R₀ is Me), ethoxylated 10bisphenol A diacrylate (where j+k=10, and R₀ is H), ethoxylated 10bisphenol A dimethacrylate (where j+k=10, and R₀ is Me), ethoxylated 30bisphenol A diacrylate (where j+k=30, and R₀ is H), ethoxylated 30bisphenol A dimethacrylate (where j+k=30, and R₀ is Me). These compoundsare commercially available from Sartomer Company under the trade namesPRO-631, SR-348, SR-349, SR-601, CD-540, CD-541, CD-542, SR-602, SR-480,SR-9038, and SR-9036 respectively. Other ethoxylated bisphenol Adimethacrylates include ethoxylated 3 bisphenol A dimethacrylate (wherej+k=3, and R₀ is Me), ethoxylated 6 bisphenol A diacrylate (wherej+k=30, and R₀ is H), and ethoxylated 8 bisphenol A diacrylate (wherej+k=30, and R₀ is H). In all of the above described compounds Q isC(CH₃)₂.

The monomer composition preferably may also include a polyethylenicfunctional monomer. Polyethylenic functional monomers are defined hereinas organic molecules which include two or more polymerizable unsaturatedgroups. Common polymerizable unsaturated groups include vinyl, allyl,allyl carbonate, methacrylyl, acrylyl, methacrylate, and acrylate.Preferably, the polyethylenic functional monomers have the generalformula (VII) or (VII) depicted below, where each R₀ is independentlyhydrogen, halo, or a C₁-C₄ alkyl group and where A₁ is as describedabove. It should be understood that while general structures (VII) and(VIII) are depicted as having only two polymerizable unsaturated groups,polyethylenic functional monomers having three (e.g.,tri(meth)acrylates), four (e.g., tetra(meth)acrylates), five (e.g.,penta(meth)acrylates), six (e.g., hexa(meth)acrylates) or more groupsmay be used.

Preferred polyethylenic functional monomers which may be combined withan aromatic containing polyethylenic polyether functional monomer toform the monomer composition include, but are not limited to,ethoxylated 2 bisphenol A dimethacrylate,tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated 10 bisphenol Adimethacrylate, ethoxylated 4 bisphenol A dimethacrylate,dipentaerythritol pentaacrylate, 1,6-hexanediol dimethacrylate, isobomylacrylate, pentaerythritol triacrylate, ethoxylated 6 trimethylolpropanetriacrylate, and bisphenol A bis allyl carbonate.

According to one embodiment, the liquid lens forming compositionincludes ethoxylated 4 bisphenol A dimethacrylate. Ethoxylated 4bisphenol A dimethacrylate monomer, when cured to form an eyeglass lens,typically produces lenses that have a higher index of refraction thancomparable lenses produced using DEG-BAC. Lenses formed from such amid-index lens forming composition which includes ethoxylated 4bisphenol A dimethacrylate may have an index of refraction of about 1.56compared to the PRO-629 compositions (previously described) which tendto have an index of refraction of about 1.51. A lens made from a higherindex of refraction polymer may be thinner than a lens made from a lowerindex of refraction polymer because the differences in the radii ofcurvature between the front and back surface of the lens do not have tobe as great to produce a lens of a desired focal power. Lenses formedfrom a lens forming composition which includes ethoxylated 4 bisphenol Adimethacrylate may also be more rigid than lenses formed from PRO-629based compositions.

The monomer composition may include additional monomers, which, whencombined with ethoxylated 4 bisphenol A dimethacrylate, may modify theproperties of the formed eyeglass lens and/or the lens formingcomposition. Tris(2-hydroxyethyl)isocyanurate triacrylate, availablefrom Sartomer under the trade name SR-368, is a triacrylate monomer thatmay be included in the composition to provide improved clarity, hightemperature rigidity, and impact resistance properties to the finishedlens. Ethoxylated 10 bisphenol A dimethacrylate, available from Sartomerunder the trade name SR-480, is a diacrylate monomer that may beincluded in the composition to provide impact resistance properties tothe finished lens. Ethoxylated 2 bisphenol A dimethacrylate, availablefrom Sartomer under the trade name SR-348, is a diacrylate monomer thatmay be included in the composition to provide tintability properties tothe finished lens. Dipentaerythritol pentaacrylate, available fromSartomer under the trade name SR-399,is a pentaacrylate monomer that maybe included in the composition to provide abrasion resistance propertiesto the finished lens. 1,6-hexanediol dimethacrylate, available fromSartomer under the trade name SR-239,is a diacrylate monomer that may beincluded in the composition to reduce the viscosity of the lens formingcomposition. Isobomyl acrylate, available from Sartomer under the tradename SR-506,is an acrylate monomer that may be included in thecomposition to reduce the viscosity of the lens forming composition andenhance tinting characteristics. Bisphenol A bis allyl carbonate may beincluded in the composition to control the rate of reaction during cureand also improve the shelf life of the lens forming composition.Pentaerythritol triacrylate, available from Sartomer under the tradename SR-444, is a triacrylate monomer that may be included in thecomposition to promote better adhesion of the lens forming compositionto the molds during curing. Ethoxylated 6 trimethylolpropanetriacrylate, available from Sartomer under the trade name SR-454, mayalso be added.

Photoinitiators which may be used in the lens forming composition havebeen described in previous sections. In one embodiment, thephotoinitiator composition preferably includesbis(2,6-dimethoxybenzoyl)-(2,4,4-trimethylphenyl)phosphine oxide(IRG-819) which is commercially available from Ciba Additives under thetrade name of Irgacure 819. The amount of Irgacure 819 present in a lensforming composition preferably ranges from about 30 ppm by weight toabout 2000 ppm by weight. In another embodiment, the photoinitiatorcomposition may include a mixture of photoinitiator. Preferably, amixture of Irgacure 819 and 1-hydroxycyclohexylphenyl ketone,commercially available from Ciba Additives under the trade name ofIrgacure 184 (IRG-184), is used. Preferably, the total amount ofphotoinitiators in the lens forming composition ranges from about 50 ppmto about 1000 ppm.

In another embodiment, an ophthalmic eyeglass lens may be made from lensforming composition comprising a monomer composition, a photoinitiatorcomposition, and a co-initiator composition. The lens formingcomposition, in liquid form, is preferably placed in a mold cavitydefined by a first mold member and a second mold member. It is believedthat activating light which is directed toward the mold members toactivate the photoinitiator composition causes the photoinitiator toform a polymer chain radical. The co-initiator may react with a fragmentor an active species of either the photoinitiator or the polymer chainradical to produce a monomer initiating species. The polymer chainradical and the monomer initiating species may react with the monomer tocause polymerization of the lens forming composition.

The monomer composition preferably includes an aromatic containingpolyethylenic polyether functional monomer having a structure as shownabove. Preferably, the polyethylenic functional monomer is an aromaticpolyether polyethylenic functional monomer containing at least one groupselected from acrylyl or methacrylyl.

More preferably, the polyethylenic functional monomer is an ethoxylatedbisphenol A di(meth)acrylate. The monomer composition may include amixture of polyethylenic functional monomers, as described above. Thephotoinitiators which may be present in the lens forming compositionhave been described above.

The lens forming composition preferably includes a co-initiatorcomposition. The co-initiator composition preferably includes amineco-initiators. Amines are defined herein as compounds of nitrogenformally derived from ammonia (NH₃) by replacement of the hydrogens ofammonia with organic substituents. Co-initiators include acrylyl amineco-initiators commercially available from Sartomer Company under thetrade names of CN-381, CN-383, CN-384, and CN-386, where theseco-initiators are monoacrylyl amines, diacrylyl amines, or mixturesthereof. Other co-initiators include ethanolamines. Examples ofethanolamines include but are not limited to N-methyldiethanolamine(NMDEA) and triethanolamine (TEA) both commercially available fromAldrich Chemicals. Aromatic amines (e.g., aniline derivatives) may alsobe used as co-initiators. Example of aromatic amines include, but arenot limited to, ethyl-4-dimethylaminobenzoate (E-4-DMAB),ethyl-2-dimethylaminobenzoate (E-2-DMAB),n-butoxyethyl-4-dimethylaminobenzoate, p-dimethylaminobenzaldehyde, N,N-dimethyl-p-toluidine, and octyl-p-(dimethylamino)benzoate commerciallyavailable from Aldrich Chemicals or The First Chemical Group ofPascagoula, Miss.

Preferably, acrylated amines are included in the co-initiatorcomposition. Acrylyl amines may have the general structures depicted inFIG. 39, where R₀ is hydrogen or methyl, n and m are 1 to 20, preferably1-4, and R₁ and R₂ are independently alkyl containing from 1 to about 4carbon atoms or phenyl. Monoacrylyl amines may include at least oneacrylyl or methacrylyl group (see compounds (A) and (B) in FIG. 39).Diacrylyl amines may include two acrylyl, two methacrylyl, or a mixtureof acrylyl or methacrylyl groups (see compounds (C) and (D) in FIG. 39).Acrylyl amines are commercially available from Sartomer Company underthe trade names of CN-381, CN-383, CN-384, and CN-386, where theseco-initiators are monoacrylyl amines, diacrylyl amines, or mixturesthereof. Other acrylyl amines include dimethylaminoethyl methacrylateand dimethylaminoethyl acrylate both commercially available fromAldrich. In one embodiment, the co-initiator composition preferablyincludes a mixture of CN-384 and CN-386. Preferably, the total amount ofco-initiators in the lens forming composition ranges from about 50 ppmto about 7% by weight.

An advantage to lens forming compositions which include a co-initiatoris that less photoinitiator may be used to initiate curing of the lensforming composition. Typically, plastic lenses are formed from a lensforming composition which includes a photoinitiator and a monomer. Toimprove the hardness of the formed lenses the concentration ofphotoinitiator may be increased. Increasing the concentration ofphotoinitiator, however, may cause increased yellowing of the formedlens, as has been described previously. To offset this increase inyellowing, a permanent dye may be added to the lens forming composition.As the amount of yellowing is increased the amount of dye added may alsobe increased. Increasing the concentration of the dye may cause thelight transmissibility of the lens to decrease.

A lens forming composition that includes a co-initiator may be used toreduce the amount of photoinitiator used. To improve the hardness of theformed lenses a mixture of photoinitiator and co-initiator may be usedto initiate curing of the monomer. The above-described co-initiatorstypically do not significantly contribute to the yellowing of the formedlens. By adding co-initiators to the lens forming composition, theamount of photoinitiator may be reduced. Reducing the amount ofphotoinitiator may decrease the amount of yellowing in the formed lens.This allows the amount of dyes added to the lens forming composition tobe reduced and light transmissibility of the formed lens may be improvedwithout sacrificing the rigidity of the lens.

The lens forming composition may also include activating light absorbingcompounds. These compounds may absorb at least a portion of theactivating light which is directed toward the lens forming compositionduring curing. One example of activating light absorbing compounds arephotochromic compounds. Photochromic compounds which may be added to thelens forming composition have been previously described. Preferably, thetotal amount of photochromic compounds in the lens forming compositionranges from about 1 ppm to about 1000 ppm. Examples of photochromiccompounds which may be used in the lens forming composition include, butare not limited to Corn Yellow, Berry Red, Sea Green, Plum Red,Variacrol Yellow, Palatinate Purple, CH-94, Variacrol Blue D, OxfordBlue and CH-266. Preferably, a mixture of these compounds is used.Variacrol Yellow is a napthopyran material, commercially available fromGreat Lakes Chemical in West Lafayette, Ind. Corn Yellow and Berry Redare napthopyrans and Sea Green, Plum Red and Palatinate Purple arespironaphthoxazine materials commercially available from KeystoneAniline Corporation in Chicago, Ill. Variacrol Blue D and Oxford Blueare spironaphthoxazine materials, commercially available from GreatLakes Chemical in West Lafayette, Ind. CH-94 and CH-266 are benzopyranmaterials, commercially available from Chroma Chemicals in Dayton, Ohio.The composition of a Photochromic Dye Mixture which may be added to thelens forming composition is described in the table below.

Photochromic Dye Mixture Corn Yellow 22.3% Berry Red 19.7% Sea Green14.8% Plum Red 14.0% Variacrol Yellow 9.7% Palatinate Purple 7.6% CH-944.0% Variacrol Blue D 3.7% Oxford Blue 2.6% CH-266 1.6%

The lens forming composition may also other activating light absorbingcompounds such as UV stabilizers, UV absorbers, and dyes. UVstabilizers, such as Tinuvin 770 may be added to reduce the rate ofdegradation of the formed lens caused by exposure to ultraviolet light.UV absorbers, such as2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol, may beadded to the composition to provide UV blocking characteristics to theformed lens. Small amounts of dyes, such as Thermoplast Blue 684 andThermoplast Red from BASF may be added to the lens forming compositionto counteract yellowing. These classes of compounds have been describedin greater detail in previous sections.

In an embodiment, a UV absorbing composition may be added to the lensforming composition. The UV absorbing composition preferably includes aphotoinitiator and a UV absorber. Photoinitiators and UV absorbers havebeen described in greater detail in previous sections. Typically, theconcentration of UV absorber in the lens forming composition required toachieve desirable UV blocking characteristics is in the range from about0.1 to about 0.25% by weight. For example,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol may beadded to the lens forming composition as a UV absorber at aconcentration of about 0.17%.

By mixing a photoinitiator with a UV absorbing compound the combinedconcentration of the photoinitiator and the UV absorber required toachieve the desired UV blocking characteristics in the formed lens maybe lower than the concentration of UV absorber required if used alone.For example,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol may beadded to the lens forming composition as a UV absorber at aconcentration of about 0.17% to achieve the desired UV blockingcharacteristics for the formed lens. Alternatively, a UV absorbingcomposition may be formed by a combination of2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol with thephotoinitiator 2-isopropyl-thioxanthone (ITX), commercially availablefrom Aceto Chemical in Flushing, N.Y. To achieve similar UV blockingcharacteristics in the formed lens, significantly less of the UVabsorbing composition may be added to the lens forming composition,compared to the amount of UV absorber used by itself. For example,2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol at aconcentration of about 700 ppm, with respect to the lens formingcomposition, along with 150 ppm of the photoinitiator2-isopropyl-thioxanthone (2-ITX) may be used to provide UV blockingcharacteristics. Thus, a significant reduction, (e.g., from 0.15% downto less than about 1000 ppm), in the concentration of UV absorber may beachieved, without a reduction in the UV blocking ability of thesubsequently formed lens. An advantage of lowering the amount of UVabsorbing compounds present in the lens forming composition is that thesolubility of the various components of the composition may be improved.

The tables below list some examples of mid-index lens formingcompositions. The UV absorber is2-(2H-benzotriazol-2-yl)-4-(1,1,3,3,-tetramethylbutyl)phenol.

Ingredient Formula 1 Formula 2 Formula 3 Formula 4 Formula 5 Formula 6Irgacure 819 694.2 ppm 486 ppm 480 ppm 382 ppm 375 ppm 414 ppm Irgacure184 CN 384 0.962% 0.674% 0.757% 0.62% 0.61% 0.66% CN386 0.962% 0.674%0.757% 0.62% 0.61% 0.66% SR-348 97.98% 68.65% 98.2% 81.2% 79.6% 86.4%SR-368 SR-480 29.95% CD-540 SR-399 SR-239 2.0% 2.08% SR-506 CR-73 17.2%16.9% 10.0% PRO-629 Tinuvin 770 290 ppm UV Absorber 0.173% Thermoplast0.534 ppm 0.374 ppm 0.6 ppm 0.5 ppm 4.5 ppm 4.58 ppm Blue Thermoplast0.019 ppm 0.0133 0.015 ppm 0.012 ppm 0.58 ppm 0.58 ppm Red ppm MineralOil 136 ppm 65 ppm Photochromic 470 ppm 507 ppm Dye Mixture IngredientFormula 7 Formula 8 Formula 9 Formula 10 Formula 11 Formula 12 Irgacure819 531.2 ppm 462 ppm 565.9 ppm 226 ppm 443 ppm 294 ppm Irgacure 18418.7 ppm 144 ppm CN 384 0.77% 0.887% 0.78% 0.40% 0.61% CN386 0.77%0.887% 0.78% 0.53% 0.61% SR-348 72.4% 70.36% 58.20% 41.5% 88.70% SR-36824.1% 23.87% 21.4% 7.0% SR-480 CD-540 18.7% 0.74% 97.76% SR-399 46.8%SR-239 1.86% 3.65% 20.1% 2.00% SR-506 10.0% CR-73 20.1% 2.9% PRO-6290.05% Tinuvin 770 UV Absorber Thermoplast 0.567 ppm 3.62 ppm 0.70 ppm0.255 ppm 0.6 ppm 4.3 ppm Blue Thermoplast 0.0147 ppm 0.576 ppm 0.014ppm 0.006 ppm 0.028 ppm 0.24 ppm Red Photochromic 450 ppm Dye MixtureIngredient Formula 13 Formula 14 Formula 15 Formula 16 Formula 17Formula 18 Irgacure 819 760 ppm 620 ppm 289 ppm 105 ppm 343 ppm Irgacure184 CN 384 0.73% 0.34% 0.475% CN 386 0.73% 0.34% 1.00% 0.70% 0.475%2-ITX 188 ppm 141 ppm SR-348 89.00% 92.00% 98.90% SR-368 SR-480 CD-54097.57% 96.20% 99.28% 0.34% SR-399 SR-239 2.30% 2.30% 0.01% SR-506 SR-444SR-454 10.00% 6.9% CR-73 PRO-629 Tinuvin 770 UV Absorber 785 ppmThermoplast 4.9 ppm 5.1 ppm 0.508 ppm 0.35 ppm 0.69 ppm Blue Thermoplast0.276 ppm 0.285 ppm 0.022 ppm 0.002 ppm 0.034 ppm Red Dioctyl- 125 ppmphthalate Butyl stearate Photochromic 499 ppm Dye Mixture IngredientFormula 19 Formula 20 Formula 21 Formula 22 Formula 23 Formula 24Irgacure 819 490 ppm 635 ppm 610 ppm 735 ppm 320 ppm 600 ppm Irgacure184 CN 384 0.680% 0.746% 0.705% 0.60% CN 386 0.680% 0.746% 0.705% 0.60%2-ITX SR-348 69.30% 68.60% SR-368 74.0% 22.10% SR-480 CD-540 98.45%92.60% 98.50% 1.0% 1.97% SR-399 SR-239 0.01% 3.86% 0.16% SR-506 0.10%SR-444 29.30% SR-454 25.0% 7.40% CR-73 PRO-629 0.007% 2.06% Tinuvin 770UV Absorber Thermoplast 0.37 ppm 0.507 ppm 3.07 ppm 4.3 ppm 0.15 ppm0.29 ppm Blue Thermoplast 0.013 ppm 0.0126 ppm 0.336 ppm 0.41 ppm 0.006ppm 0.012 ppm Red Dioctyl- phthalate Butyl stearate Photochromic 442 ppm497 ppm Dye Mixture Ingredient Formula 25 Formula 26 Formula 27 Formula28 Formula 29 Formula 30 Formula 31 Irgacure 819 650 ppm 464 ppm 557 ppm448 ppm 460 ppm Irgacure 184 300 ppm CN 384 0.650% 0.70% CN 386 0.650%0.70% 2-ITX 600 ppm 120 ppm SR-348 39.10% SR-368 13.00% 19.60% 20.70%SR-480 10.70% CD-540 88.96% 41.90% 1.60% 1.30% 99.94% 99.96% SR-399SR-239 SR-506 98.30% 79.00% 67.24% SR-444 9.70% 4.60% SR-454 CR-73PRO-629 Tinuvin 770 UV Absorber Thermoplast 0.566 ppm 0.52 ppm 0.24 ppm0.19 ppm 0.467 ppm Blue Thermoplast 0.02 ppm 0.013 ppm 0.01 ppm 0.008ppm 0.024 ppm Red Dioctyl- phthalate Butyl stearate 75 ppm 35 ppmPhotochromic Dye Mixture

In one embodiment, plastic lenses may be formed by disposing a mid-indexlens forming composition into the mold cavity of a mold assembly andirradiating the mold assembly with activating light. Coating materialsmay be applied to the mold members prior to filling the mold cavity withthe lens forming composition.

After filing the mold cavity of the mold assembly the mold assembly ispreferably placed in the lens curing unit and subjected to activatinglight. Preferably, actinic light is used to irradiate the mold assembly.A clear polycarbonate plate may be placed between the mold assembly andthe activating light source. The polycarbonate plate preferably isolatesthe mold assembly from the lamp chamber, thus preventing airflow fromthe lamp cooling fans from interacting with the mold assemblies. Theactivating light source may be configured to deliver from about 0.1 toabout 10 milliwatts/cm² to at least one non-casting face, preferablyboth non-casting faces, of the mold assembly. Depending on thecomponents of the lens forming composition used the intensity ofactivating light used may be <1 milliwatt/cm². The intensity of incidentlight at the plane of the lens curing unit drawer is measured using anInternational Light IL-1400 radiometer equipped with an XRL140A detectorhead. This particular radiometer preferably has a peak detectionwavelength at about 400 nm, with a detection range from about 310 nm toabout 495 nm. The International Light IL-1400 radiometer and the XRL140Adetector head are both commercially available International Light,Incorporated of Newburyport, Mass.

After the mold assembly is placed within the lens curing unit, the moldassemblies are preferably irradiated with activating light continuouslyfor 30 seconds to thirty minutes, more preferably from one minute tofive minutes. Preferably, the mold assemblies irradiated in the absenceof a cooling air stream. After irradiation, the mold assemblies wereremoved from the lens curing unit and the formed lens demolded. Thelenses may be subjected to a post-cure treatment in the post-cure unit.

In general, it was found that the use of a photoinitiator (e.g., IRG-819and IRG-184) in the lens forming composition produces lenses with bettercharacteristics than lens formed using a co-initiator only. For example,formula 15, described in the above table, includes a monomer composition(a mixture of SR-348 and SR-454)and a co-initiator (CN-386). When thislens forming composition was exposed to activating light for 15 min.there was no significant reaction or gel formation. It is believed thatthe co-initiator requires an initiating species in order to catalyzecuring of the monomer composition. Typically this initiating species isproduced from the reaction of the photoinitiator with activating light.

A variety of photoinitiators and photoinitiators combined withco-initiators may be used to initiate polymerization of the monomercomposition. One initiator system which may be used includesphotoinitiators IRG-819 and 2-ITX and a co-initiator, see Formulas17-18. Such a system is highly efficient at initiating polymerizationreactions. The efficiency of a polymerization catalyst is a measurementof the amount of photoinitiator required to initiate a polymerizationreaction. A relatively small amount of an efficient photoinitiator maybe required to catalyze a polymerization reaction, whereas a greateramount of a less efficient photoinitiator may be required to catalyzethe polymerization reaction. The IRG-819/2-ITX/co-initiator system maybe used to cure lenses forming compositions which include a UV absorbingcompound. This initiator system may also be used to form colored lenses.

An initiator system that is less efficient than theIRG-819/2-ITX/co-initiator system includes a mixture of thephotoinitiators IRG-819 and 2-ITX, see Formula 31. This system is lessefficient at initiating polymerization of lens forming compositions thanthe IRG-819/2-ITX/co-initiator system. The IRG-819/2-ITX system may beused to cure very reactive monomer compositions. An initiator systemhaving a similar efficiency to the IRG-819/2-ITX system includes amixture of IRG-819 and co-initiator, see Formulas 1-6, 8-9, 11, 14-15,19-22, and 25-26. The IRG-819/co-initiator system may be used to cureclear lenses which do not include a UV blocking compound andphotochromic lens forming compositions.

Another initiator system which may be used includes the photoinitiator2-ITX and a co-initiator. This initiator system is much less efficientat initiating polymerization reactions than the IRG-819/co-initiatorsystem. The 2-ITX/co-initiator system is preferably used for curingmonomer compositions which include highly reactive monomers.

The use of the above described mid-index lens forming compositions mayminimize or eliminate a number of problems associated with activatinglight curing of lenses. One problem typical of curing eyeglass lenseswith activating light is pre-release. Pre-release may be caused by anumber of factors. If the adhesion between the mold faces and theshrinking lens forming composition is not sufficient, pre-release mayoccur. The propensity of a lens forming composition to adhere to themold face, in combination with its shrinkage, determine how the processvariables are controlled to avoid pre-release. Adhesion is affected bysuch factors as geometry of the mold face (e.g., high-add flattopbifocals tend to release because of the sharp change in cavity height atthe segment line), the temperature of the mold assembly, and thecharacteristics of the in-mold coating material. The process variableswhich are typically varied to control pre-release include theapplication of cooling fluid to remove exothermic heat, controlling therate of heat generation by manipulating the intensities and timing ofthe activating radiation, providing differential light distributionacross the thin or thick sections of the mold cavity manipulating thethickness of the molds, and providing in-mold coatings which enhanceadhesion. An advantage of the above described mid-index lens formingcompositions is that the composition appears to have enhanced adhesioncharacteristics. This may allow acceptable lenses to be produced over agreater variety of curing conditions. Another advantage is that higherdiopter lenses may be produced at relatively low pre-release rates,broadening the achievable prescription range.

Another advantage of the above described mid-index lens formingcompositions is that they tend to minimize problems associated withdripping during low intensity curing of lenses (e.g., in the 1 to 6milliwatt range). Typically, during the irradiation of the lens formingcomposition with activating light, small amounts of monomer may besqueezed out of the cavity and run onto the non-casting faces of themolds. Alternatively, during filling of the mold assembly with the lensforming composition, a portion of the lens forming composition may driponto the non-casting faces of the mold assembly. This “dripping” ontothe non-casting faces of the mold assembly tends to cause the activatinglight to focus more strongly in the regions of the cavity locatedunderneath the drippings. This focusing of the activating light mayaffect the rate of curing. If the rate of curing underneath thedrippings varies significantly from the rate of curing throughout therest of the lens forming composition, optical distortions may be createdin the regions below the drippings.

It is believed that differences in the rate of gelation between thecenter and the edge regions of the lens forming composition may causedripping to occur. During the curing of a lens forming composition, thematerial within the mold cavity tends to swell slightly during the gelphase of the curing process. If there is enough residual monomer aroundthe gasket lip, this liquid will tend to be forced out of the cavity andonto the non-casting faces of the mold. This problem tends to beminimized when the lens forming composition undergoes fast, uniformgelation. Typically, a fast uniform gelation of the lens formingcomposition may be achieved by manipulating the timing, intensities, anddistribution of the activating radiation. The above described mid-indexlens forming compositions, however, tend to gel quickly and uniformlyunder a variety of curing conditions, thus minimizing the problemscaused by dripping.

Another advantage of the above described mid-index lens formingcompositions is that the compositions tend to undergo uniform curingunder a variety of curing conditions. This uniform curing tends tominimize optical aberrations within the formed lens. This is especiallyevident during the formation of high plus power flattop lenses whichtend to exhibit optical distortions after the lens forming compositionis cured. It is believed that the activating radiation may be reflectedoff of the segment line and create local differences in the rate ofgelation in the regions of the lens forming composition that thereflected light reaches. The above described mid-index lens formingcompositions tend to show less optical distortions caused by variationsof the intensity of activating radiation throughout the composition.

Other advantages include drier edges and increased rigidity of theformed lens. An advantage of drier edges is that the contamination ofthe optical faces of the lens by uncured or partially cured lens formingcomposition is minimized.

METHODS OF FORMING PLASTIC LENSES

Plastic lenses may be formed by disposing a lens forming compositioninto the mold cavity of a mold assembly and irradiating the moldassembly with activating light. Coating materials may be applied to themold members prior to filling the mold cavity with the lens formingcomposition. The lens may be treated in a post-cure unit after thelens-curing process is completed.

The operation of the above described system to provide plastic lensesinvolves a number of operations. These operations are preferablycoordinated by the controller 50, which has been described above. Afterpowering the system, an operator is preferably signaled by thecontroller to enter the prescription of the lens, the type of lens, andthe type of coating materials for the lens. Based on these inputtedvalues the controller will preferably indicate to the operator whichmolds and gaskets will be required to form the particular lens.

After obtaining the appropriate mold members the mold members arepreferably cleaned prior to loading with a lens forming composition. Theinner surface (i.e., casting surface) of the mold members may be cleanedon a spin coating unit 20 by spraying the mold members with a cleaningsolution while spinning the mold members. Examples of cleaning solutionsinclude methanol, ethanol, isopropyl alcohol, acetone, methyl ethylketone, or a water based detergent cleaner. Preferably, a cleaningsolution which includes isopropyl alcohol is used to clean the moldmembers. As the mold member is contacted with the cleaning solution,dust and dirt may be removed and transferred into the underlying dish115 of the curing unit. After a sufficient amount of cleaning solutionhas been applied the mold members may be dried by continued spinningwithout the application of cleaning solution.

In an embodiment, the inner surface, i.e., the casting face, of thefront mold member may be coated with one or more hardcoat layers beforethe lens forming composition is placed within the mold cavity.Preferably, two hardcoat layers are used so that any imperfections, suchas pin holes in the first hardcoat layer, are covered by the secondhardcoat layer. The resulting double hardcoat layer is preferablyscratch resistant and protects the subsequently formed eyeglass lens towhich the double hardcoat layer adheres. The hardcoat layers arepreferably applied using a spin coating unit 20. The mold member ispreferably placed in the spin coating unit and the coating materialapplied to the mold while spinning at high speeds (e.g., between about900 to 1000 RPM). After a sufficient amount of coating material has beenapplied, the coating material may be cured by the activating lightsource disposed in the cover. The cover is preferably closed andactivating light is preferably applied to the mold member while the moldmember is spinning at relatively low speeds (e.g., between about 150 to250 RPM). Preferably control of the spinning and the application ofactivating light is performed by controller 50. Controller 50 ispreferably configured to prompt the operator to place the mold memberson the coating unit, apply the coating material to the mold member, andclose the cover to initiate curing of the coating material.

In an embodiment, the eyeglass lens that is formed may be coated with ahydrophobic layer, e.g. a hardcoat layer. The hydrophobic layerpreferably extends the life of the photochromic pigments near thesurfaces of the lens by preventing water and oxygen molecules fromdegrading the photochromic pigments.

In a preferred embodiment, both mold members may be coated with a curedadhesion-promoting composition prior to placing the lens formingcomposition into the mold cavity. Providing the mold members with suchan adhesion-promoting composition is preferred to increase the adhesionbetween the casting surface of the mold and the lens formingcomposition. The adhesion-promoting composition thus reduces thepossibility of premature release of the lens from the mold. Further, itis believed that such a coating also provides an oxygen and moisturebarrier on the lens which serves to protect the photochromic pigmentsnear the surface of the lens from oxygen and moisture degradation. Yetfurther, the coating provides abrasion resistance, chemical resistance,and improved cosmetics to the finished lens.

In an embodiment, the casting face of the back mold member may be coatedwith a material that is capable of being tinted with dye prior tofilling the mold cavity with the lens forming composition. This tintablecoat preferably adheres to the lens forming composition so that dyes maylater be added to the resulting eyeglass lens for tinting the lens. Thetintable coat may be applied using the spin coating unit as describedabove.

The controller may prompt the user to obtain the appropriate lensforming composition. In one embodiment, the controller will inform theuser of which chemicals and the amounts of each chemical that isrequired to prepare the lens forming composition. Alternatively, thelens forming compositions may be preformed. In this case the controllermay indicate to the operator which of the preformed lens formingcompositions should be used.

In an embodiment, dyes may be added to the lens forming composition. Itis believed that certain dyes may be used to attack and encapsulateambient oxygen so that the oxygen may be inhibited from reacting withfree radicals formed during the curing process. Also, dyes may be addedto the composition to alter the color of an unactivated photochromiclens. For instance, a yellow color that sometimes results after a lensis formed may be “hidden” if a blue-red or blue-pink dye is present inthe lens forming composition. The unactivated color of a photochromiclens may also be adjusted by the addition of non-photochromic pigmentsto the lens forming composition.

In a preferred technique for filling the lens molding cavity 382 (seeFIG. 11), the annular gasket 380 is placed on a concave or front moldmember 392 and a convex or back mold member 390 is moved into place. Theannular gasket 380 is preferably pulled away from the edge of the backmold member 390 at the uppermost point and a lens forming composition ispreferably injected into the lens molding cavity 382 until a smallamount of the lens forming composition is forced out around the edge.The excess is then removed, preferably, by vacuum. Excess liquid that isnot removed could spill over the face of the back mold member 390 andcause optical distortion in the finished lens.

The mold assembly, with a lens forming composition disposed within themold cavity, is preferably placed within the lens curing unit. Curing ofthe lens forming composition is preferably initiated by the controllerafter the lens curing unit door is closed. The curing conditions arepreferably set by the controller based on the prescription and type oflens being formed.

After the curing cycle has been completed. The controller preferablyprompts the user to remove the mold assembly from the lens curing unit.In an embodiment, the cured lens may be removed from the mold apparatus.The cured lens may be complete at this stage and ready for use.

In another embodiment, the cured lens may require a post cure treatment.After the lens is removed from the mold apparatus the edges of the lensmay be dried and scraped to remove any uncured lens forming compositionnear the edges. The controller may prompt the user to place thepartially cured lens into a post-cure unit. After the lens has beenplaced within the post-cure unit the controller may apply light and/orheat to the lens to complete the curing of the lens. In an embodiment,partially cured lenses may be heated to about 115° C. while beingirradiated with activating light. This post-treatment may be applied forabout 5 minutes.

When casting a lens, particularly a positive lens that is thick in thecenter, cracking may be a problem. Addition polymerization reactions,including photochemical addition polymerization reactions, may beexothermic. During the process, a large temperature gradient may buildup and the resulting stress may cause the lens to crack. Yellowing ofthe finished lens may also be a problem. Yellowing tends to be relatedto the monomer composition, the identity of the photoinitiator, and theconcentration of the photoinitiator.

The formation of optical distortions usually occurs during the earlystages of the polymerization reaction during the transformation of thelens forming composition from the liquid to the gel state. Once patternsleading to optical distortions form they may be difficult to eliminate.When gelation occurs there typically is a rapid temperature rise. Theexothermic polymerization step causes a temperature increase, which inturn causes an increase in the rate of polymerization, which causes afurther increase in temperature. If the heat exchange with thesurroundings is not sufficient to cool the lens, there will be a runawaysituation that leads to premature release, the appearance of thermallycaused striations and even breakage.

Accordingly, when continuous activating light is applied, it ispreferred that the reaction process be smooth and not too fast but nottoo slow. Heat is preferably not generated by the process so fast thatit may not be exchanged with the surroundings. The incident activatinglight intensity is preferably adjusted to allow the reaction to proceedat a desired rate. It is also preferred that the seal between theannular gasket 380 and the opposed mold members 378 be as complete aspossible.

Factors that have been found to lead to the production of lenses thatare free from optical distortions may be (1) achieving a good sealbetween the annular gasket 380 and the opposed mold members 378; (2)using mold members 378 having surfaces that are free from defects; (3)using a formulation having an appropriate type and concentration ofphotoinitiator that will produce a reasonable rate of temperature rise;and (4) using a homogeneous formulation. Preferably, these conditionsare optimized.

Premature release of the lens from the mold will result in anincompletely cured lens and the production of lens defects. Factors thatcontribute to premature release may be (1) a poorly assembled moldassembly 352; (2) the presence of air bubbles around the sample edges;(3) imperfection in gasket lip or mold edge; (4) inappropriateformulation; (5) uncontrolled temperature rise; and (6) high ornon-uniform shrinkage. Preferably, these conditions are minimized.

Premature release may also occur when the opposed mold members 378 areheld too rigidly by the annular gasket 380. Preferably, there issufficient flexibility in the annular gasket 380 to permit the opposedmold members 378 to follow the lens as it shrinks. Indeed, the lens mustbe allowed to shrink in diameter slightly as well as in thickness. Theuse of an annular gasket 380 that has a reduced degree of stickinesswith the lens during and after curing is therefore desirable.

Despite the above problems, the advantages offered by the radiationcured lens molding system clearly outweigh the disadvantages. Theadvantages of a radiation cured system include a significant reductionin energy requirements, curing time and other problems normallyassociated with conventional thermal systems.

1. Method of Forming a Plastic Lens by Curing with Activating Light

In one embodiment, plastic lenses may be formed by disposing a lensforming composition into the mold cavity of a mold assembly andirradiating the mold assembly with activating light. Coating materialsmay be applied to the mold members prior to filling the mold cavity withthe lens forming composition. The lens may be treated in a post-cureunit after the lens-curing process is completed.

The lens forming composition is preferably prepared according to thefollowing protocol. Appropriate amounts of HDDMA, TTEGDA, IMPTA andTRPGDA are mixed and stirred thoroughly, preferably with a glass rod.The acrylate/methacrylate mixture may then be passed through apurification column.

A suitable purification column may be disposed within a glass columnhaving a fitted glass disk above a Teflon stopcock and having a topreservoir with a capacity of approximately 500 ml and a body with adiameter of 22 mm and a length of about 47 cm. The column may beprepared by placing on the fitted glass disk approximately 35 g. ofactivated alumina (basic), available from ALFA Products, JohnsonMatthey, Danvers, MA in a 60 mesh form or from Aldrich in a 150 meshform. Approximately 10 g. of an inhibitor remover(hydroquinone/methylester remover) available as HR-4 from ScientificPolymer Products, Inc., Ontario, N.Y. then may be placed on top of thealumina and, finally, approximately 35 g. of activated alumina (basic)may be placed on top of the inhibitor remover.

Approximately 600 g. of the acrylate/methacrylate mixture may then beadded above the column packing. An overpressure of 2-3 psi may then beapplied to the top of the column resulting in a flow rate ofapproximately 30 to 38 grams per hour. Parafilm may be used to cover thejunction of the column tip and the receiving bottle to prevent theinfiltration of dust and water vapor. The acrylate/methacrylate mixture,preferably, may be received in a container that is opaque to activatinglight.

An appropriate amount of bisphenol A bis(allyl carbonate) may then beadded to the acrylate/methacrylate mixture to prepare the final monomermixture.

An appropriate amount of a photoinitiator may then be added to the finalmonomer mixture. The final monomer mixture, with or withoutphotoinitiator, may then be stored in a container that is opaque toactivating light.

An appropriate amount of a dye may also be added to the final monomermixture, with or without photoinitiator.

After filling the mold cavity with the lens forming composition, themold assembly is preferably irradiated with activating light. In oneembodiment, the lamps generate an intensity at the lamp surface ofapproximately 4.0 to 7.0 mW/cm² of ultraviolet light having wavelengthsbetween 300 and 400 nm, which light is very uniformly distributedwithout any sharp discontinuities throughout the reaction process. Suchbulbs are commercially available from Sylvania under the tradedesignation Sylvania Fluorescent (F15T8/2052) or Sylvania Fluorescent(F15T8/350BL/18″) GTE. Activating light having wavelengths between 300and 400 nm is preferred because the photoinitiators preferably absorbmost efficiently at this wavelength and the mold members 378,preferably, allow maximum transmission at this wavelength. It ispreferred that there be no sharp intensity gradients of activating lighteither horizontally or vertically through the lens composition duringthe curing process. Sharp intensity gradients through the lens may leadto defects in the finished lens.

If lenses are produced with continuous activating light without any moldcooling, the temperature of the mold-lens assembly may rise to above 50°C. Low diopter lenses may be prepared in this fashion, but higher plusor minus diopter lenses may fail. Certain lenses may be made bycontrolling (e.g., cooling) the temperature of the lens material duringcure with circulating uncooled fluid (i.e., fluid at ambienttemperatures). The ambient fluid in these systems is preferably directedtowards the mold members in the same manner as described above.Circulating ambient temperature fluid permits manufacture of a widerrange of prescriptions than manufacture of the lenses without any moldcooling at all.

Many polymerization factors may be interrelated. The ideal temperatureof polymerization is typically related to the diopter and thickness ofthe lens being cast. Lower temperatures (below about 10° C.) arepreferred to cast higher + or − diopter lenses when using continuousactivating light. These lower temperatures tend to permit an increase inphotoinitiator concentration, which in turn may speed up the reactionand lower curing time.

Preventing premature release when using continuous activating light mayalso be somewhat dependent upon the flow rates of cooling fluid, as wellas its temperature. For instance, if the temperature of the coolingfluid is decreased it may also be possible to decrease the flowrate ofcooling fluid. Similarly, the disadvantages of a higher temperaturecooling fluid may be somewhat offset by higher flow rates of coolingfluid.

In one embodiment the air flow rates for a dual distributor system(i.e., an air distributor above and below the lens composition) areabout 1-30 standard cubic feet (“scf”) (about 0.028-0.850 standard cubicmeters, “scm”) per minute per distributor, more preferably about 4-20scf (about 0.113-0.566 scm) per minute per distributor, and morepreferably still about 9-15 scf (about 0.255-0.423 scm) per minute perdistributor. “Standard conditions,” as used herein, means 60° F. (about15.5° C.) and one atmosphere pressure (about 101 kilopascals).

The thickness of the glass molds used to cast polymerized lenses mayaffect the lenses produced. A thinner mold tends to allow more efficientheat transfer between the polymerizing material and the cooling air,thus reducing the rate of premature release. In addition, a thinner moldtends to exhibit a greater propensity to flex. A thinner mold tends toflex during the relatively rapid differential shrinkage between thethick and thin portions of a polymerized lens, again reducing theincidence of premature release. In one embodiment the first or secondmold members have a thickness less than about 5.0 mm, preferably about1.0-5.0 mm, more preferably about 2.0-4.0 mm, and more still about2.5-3.5 mm.

“Front” mold or face means the mold or face whose surface ultimatelyforms the surface of an eyeglass lens that is furthest from the eye ofan eyeglass lens wearer. “Back” mold or face means the mold or facewhose surface ultimately forms the surface of an eyeglass lens that isclosest to the eye of an eyeglass lens wearer.

In one embodiment, the lens forming material is preferably cured to forma solid lens at relatively low temperatures, relatively low continuousactivating light intensity, and relatively low photoinitiatorconcentrations. Lenses produced as such generally have a Shore Dhardness of about 60-78 (for preferred compositions) when cured forabout 15 minutes as described above. The hardness may be improved toabout 80-81 Shore D by postcure heating the lens in a conventional ovenfor about 10 minutes, as described above.

The activating light cured lenses may demonstrate excellent organicsolvent resistance to acetone, methyl ethyl ketone, and alcohols.

2. Preparing Lenses of Various Powers By Altering the Lens FormingConditions

It has been determined that in some embodiments the finished power of anactivating light polymerized lens may be controlled by manipulating thecuring temperature of the lens forming composition. For instance, for anidentical combination of mold members and gasket, the focusing power ofthe produced lens may be increased or decreased by changing theintensity of activating light across the lens mold cavity or the facesof the opposed mold members.

As the lens forming material begins to cure, it passes through a gelstate, the pattern of which, within the mold assembly, leads to theproper distribution of internal stresses generated later in the curewhen the lens forming material begins to shrink. As the lens formingmaterial shrinks during the cure, the opposed mold members willpreferably flex as a result of the different amounts of shrinkagebetween the relatively thick and the relatively thin portions of thelens. When a negative lens, for example, is cured, the upper or backmold member will preferably flatten and the lower or front mold memberwill preferably steepen with most of the flexing occurring in the loweror front mold member. Conversely, with a positive lens, the upper orback mold member will preferably steepen and the lower or front moldmember will preferably flatten with most of the flexing occurring in theupper or back mold member.

By varying the intensity of the activating light between the relativelythin and the relatively thick portions of the lens in the lens formingcavity, it is possible to create more or less total flexing. Those lightconditions which result in less flexing will tend to minimize thepossibility of premature release.

The initial curvature of the opposed mold members and the centerthickness of the lens produced may be used to compute the targeted powerof the lens. Herein, the “targeted power” of a lens is the power a lensmay have if the lens were to have a curvature and thicknesssubstantially identical to the mold cavity formed by the opposed moldmembers. The activating light conditions may be manipulated to alter thepower of the lens to be more or less than the targeted power.

By varying the amount of activating light reaching the lens mold thepolymerization rate, and therefore the temperature of the lens formingcomposition may be controlled. It has been determined that the maximumtemperature reached by the lens forming composition during and/or afteractivation by light may effect the final power of the lens. By allowingthe lens forming composition to reach a temperature higher than thetypical temperatures described in previous embodiments, but less thanthe temperature at which the formed lens will crack, the power of thelens may be decreased. Similarly, controlling the polymerization suchthat the temperature of the lens forming composition remainssubstantially below the typical temperatures described in previousembodiments, but at a sufficient temperature such that a properly curedlens is formed, the power of the lens may be increased. Similarly,increasing the temperature of the lens forming composition during curingmay decrease the power of the resulting lens.

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer and a photoinitiator, byirradiation of the lens forming composition with activating light. Thecomposition may optionally include one or more of: anultraviolet/visible light absorbing compound, a polymerizationinhibitor, a co-initiator, a hindered amine light stabilizer, and a dye.The activating light may include ultraviolet, actinic, visible orinfrared light. The lens forming composition may be treated withactivating light such that an eyeglass is formed that has a powersubstantially equal to the targeted power for a given mold cavity. Thepeak temperature of the lens forming process may be the maximumtemperature attained after the application of each pulse of activatinglight. As depicted in FIG. 40, each pulse of activating light may causethe lens forming composition to rise to a peak temperature.

After reaching this peak temperature the lens forming composition maybegin to cool until the next application of activating light. If thepeak temperature of the lens forming composition is controlled such thatthe formed lens has a power substantially equal to the targeted power,the peak temperature is referred to as the “matching temperature”. Thematching temperature may be determined by performing a series ofexperiments using the same mold cavity. In these experiments the peaktemperature attained during the process is preferably varied. Bymeasuring the power of the lenses obtained through this experiment thematching temperature range may be determined.

When the temperature of the lens forming composition is allowed to riseabove the matching temperature during treatment with activating light,the power of the lens may be substantially less than the targeted powerof the lens. Alternatively, when the temperature of the lens formingcomposition is allowed to remain below the matching temperature, thepower of the lens may be substantially greater than the targeted powerof the lens. In this manner, a variety of lenses having substantiallydifferent lens powers from the targeted power may be produced from thesame mold cavity.

When the lenses cured by the activating light are removed from theopposed mold members, they are typically under a stressed condition. Ithas been determined that the power of the lens may be brought to a finalresting power, by subjecting the lenses to a post-curing heat treatmentto relieve the internal stresses developed during the cure and cause thecurvature of the front and the back of the lens to shift. Typically, thelenses may be cured by the activating light in about 10-30 minutes(preferably about 15 minutes). The post-curing heat treatment ispreferably conducted at approximately 85-120° C. for approximately 5-15minutes. Preferably, the post-curing heat treatment is conducted at100-110° C. for approximately 10 minutes. Prior to the post-cure, thelenses generally have a lower power than the final resting power. Thepost-curing heat treatment reduces yellowing of the lens and reducesstress in the lens to alter the power thereof to a final resting power.

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer and a photoinitiator, byirradiation of the lens forming composition with activating light. Thecomposition may optionally include one or more of: anultraviolet/visible light absorbing compound, a polymerizationinhibitor, a co-initiator, a hindered amine light stabilizer, and a dye.The activating light may include ultraviolet, actinic, visible orinfrared light. The lens forming composition may be treated withactivating light such that an eyeglass is formed. The lens may be keptwithin the mold cavity formed by the mold members until the light hascompletely cured the lens forming composition. The minimum time which alens must remain in the mold cavity to produce a lens with the targetedpower, with respect to the mold cavity, is herein referred to as the“demolding time”. The demolding time may be determined by performing aseries of experiments using the same mold cavity. In these experimentsthe time that the lens is released from the mold cavity during theprocess is preferably varied. By measuring the power of the lensesobtained through these experiments the demolding time range may bedetermined.

When a formed lens is removed prior to the demolding time, the power ofthe lens may be substantially greater than the targeted power of thelens. By varying the demolding time a variety of lenses havingsubstantially greater lens powers from the targeted power may beproduced from the same mold cavity.

3. Postcure With An Oxygen Barrier Enriched With Photoinitiator

In certain applications, all of the lens forming composition may fail tocompletely cure by exposure to activating light when forming the lens.In particular, a portion of the lens forming composition proximate thegasket often remains in a liquid state following formation of the lens.It is believed that the gaskets may be often somewhat permeable to air,and, as a result, oxygen permeates them and contacts the portions of thelens forming material that are proximate the gasket. Since oxygen tendsto inhibit the polymerization process, portions of the lens formingcomposition proximate the gasket tend to remain uncured as the lens isformed.

Uncured lens forming composition proximate the gasket may be a problemfor several reasons. First, the liquid lens forming composition leavesthe edges of the cured lens in a somewhat sticky state, which makes thelenses more difficult to handle. Second, the liquid lens formingcomposition may be somewhat difficult to completely remove from thesurface of the lens. Third, liquid lens forming composition may flow andat least partially coat the surface of lenses when such lenses areremoved from the molds. This coating may be difficult to remove andmakes application of scratch resistant coatings or tinting dyes moredifficult. This coating tends to interfere with the interaction ofscratch resistant coatings and tinting dyes with the cured lens surface.Fourth, if droplets of liquid lens forming material form, these dropletsmay later cure and form a ridge or bump on the surface of the lens,especially if the lens undergoes later postcure or scratch resistantcoating processes. As a result of the above problems, often lenses mustbe tediously cleaned or recast when liquid lens forming compositionremains after the lens is formed in an initial cure process.

The problems outlined above may be mitigated if less liquid lens formingcomposition remains proximate the gasket after the lens is formed. Onemethod of lessening this “wet edge” problem relates to increasing theamount of photoinitiator present in the lens forming composition (i.e.,increasing the amount of photoinitiator in the lens forming compositionabove about 0.15 percent). Doing so, however, tends to create otherproblems. Specifically, increased photoinitiator levels tend to causeexothermic heat to be released at a relatively high rate during thereaction of the composition. Premature release and/or lens crackingtends to result. Thus it is believed that lower amounts ofphotoinitiator are preferred.

The wet edge problem has been addressed by a variety of methodsdescribed in U.S. Pat. No. 5,529,728 to Buazza et. al. Such methodsrelate to removing the gasket and applying either an oxygen barrier or aphotoinitiator enriched liquid to the exposed edge of the lens. The lensis preferably re-irradiated with sufficient activating light tocompletely dry the edge of the lens prior to demolding.

An embodiment relates to improving the methods described in U.S. Pat.No. 5,529,728 to Buazza et. al. This embodiment relates to combining anoxygen barrier with a photoinitiator. Specifically, in one embodiment anoxygen barrier 970 (e.g., a thin strip of polyethylene film or the likeas shown in FIG. 12) is preferably embedded or impregnated with aphotoinitiator 972. The oxygen barrier is preferably wrapped around theedge of a cured lens which is still encased between two molds (but withthe gasket removed). While still “in the mold,” the lens is preferablyexposed to activating light, thereby drying its edge. An improvement ofthis method over those previously disclosed is that there may be asignificant reduction in the dosage of activating light necessary tobring the lens edge to dryness.

A plastic oxygen barrier film which includes a photoinitiator may bemade by: (a) immersing a plastic film in a solution comprising aphotoinitiator, (b) removing the plastic film from the solution, and (c)drying the plastic film. The solution may include an etching agent.Preferably a surface of the plastic film is etched prior to or whileimmersing the plastic film in the solution.

In one example, thin strips (e.g., about 10 mm wide) of high densitypolyethylene film (approximately 0.013 mm thick) may be soaked in asolution of 97% acetone and 3% Irgacure 184 (a photoinitiatorcommercially available from Ciba Geigy located in Farmingdale, N.J.) forabout five minutes. The polyethylene film may be obtained from TapeSolutions, Inc. (Nashville, Tenn.). In a more preferred embodiment, 0.5%BYK-300 (a flow agent commercially available from BYK Chemie located inWallingford, Conn.) may be included in the soaking solution. It isbelieved that xylene in the BYK-300 tends to etch the surface of thefilm and make the film more receptive to absorption of the Irgacure 184.In a still more preferred embodiment, the treated polyethylene stripsmay be dipped in acetone for about ten seconds to remove excess Irgacure184. Excess photoinitiator may be seen as a white powder which coats thestrips after drying. In either case, the strips are preferably allowedto air dry before applying them to the edge of the lens as describedabove.

In one alternate embodiment, a plastic eyeglass lens may be made by thefollowing steps: (1) placing a liquid polymerizable lens formingcomposition in a mold cavity defined by a gasket, a first mold member,and a second mold member; (2) directing first activating light raystoward at least one of the mold members to cure the lens formingcomposition so that it forms a lens with a back face, edges, and a frontface, and wherein a portion of the lens forming composition proximatethe edges of the lens is not fully cured; (3) removing the gasket toexpose the edges of the lens; (4) applying an oxygen barrier whichincludes a photoinitiator around the exposed edges of the lens such thatat least a portion of the oxygen barrier photoinitiator is proximatelens forming composition that is not fully cured; and (5) directingsecond activating light rays towards the lens such that at least aportion of the oxygen barrier photoinitiator initiates reaction of lensforming composition while the oxygen barrier substantially preventsoxygen from outside the oxygen barrier from contacting at least aportion of the lens forming composition. The first and second activatinglight rays may (a) be at the same or different wavelengths and/orintensities, (b) be continuous or pulsed, and (c) be from the same ordifferent light source.

A purpose of the steps 4-5 is to reduce the amount of uncured liquidlens forming composition that is present when the lens is separated fromthe molds and/or gasket. It has been found that reducing the amount ofliquid lens forming composition may be especially advantageous if suchreduction occurs before the molds are separated from the cured lens.Separating the molds from the cured lens may cause uncured liquids to atleast partially coat the lens faces. This coating may occur when uncuredliquid lens forming composition gets swept over the faces when the moldsare separated from the lens. It is believed that curing of the lenstends to create a vacuum between the lens and the mold. Air may sweepover the mold faces to fill this vacuum when the molds are separatedfrom the lens. This air tends to take liquid lens forming compositioninto the vacuum with it.

In step 4 above, an oxygen barrier which includes a photoinitiator ispreferably applied to the edges or sides of the lens after the gasket isremoved. Preferably, this oxygen barrier is applied while the lens isstill attached to the molds. In an alternate embodiment, this oxygenbarrier is preferably applied to the edges or sides of the molds at thesame time it is applied to the sides of the lens. In a preferredembodiment, the sides of the lenses are first cleaned or wiped to removeat least a portion of the uncured liquid lens forming composition beforethe oxygen barrier is applied.

After the oxygen barrier is applied, second activating light rays may bedirected towards the lens. After the second activating light rays aredirected toward the lens, at least a portion of the liquid lens formingcomposition that was not cured in the initial cure steps may be cured.It is believed that the photoinitiator embedded in the oxygen barrierfacilitates faster and more complete curing of the uncured lens formingcomposition. As such, less second activating light rays may be employed,thereby lessening the time and energy required in this step.Furthermore, lens quality tends to be enhanced since a lower applicationof the second activating light rays tends to reduce the potential forlens yellowing.

In a preferred embodiment, substantially all of the remaining liquidlens forming composition is cured after the second activating light raysare directed toward the lens. More preferably, the lens is substantiallydry after the second activating light is directed towards the lens.

After the second activating light is directed toward the lens, the lensmay then be demolded. The lens may then be tinted. After the lens isdemolded, a scratch resistant coating may be applied to the lens. In oneembodiment, a scratch resistant coating is preferably applied to thedemolded lens by applying a liquid scratch resistant coating compositionto a face of the lens and then applying activating light rays to thisface to cure the liquid scratch resistant coating to a solid.

In an embodiment, the activating light for curing the scratch resistantcoating is ultraviolet light. The intensity of the activating lightapplied to the face of the lens to cure the liquid scratch resistantcoating composition to a solid is preferably about 150-300 mW/cm² at awavelength range of about 360-370 nm, and about 50-150 mW/cm² at awavelength range of about 250-260 nm. The lens may be heated afterremoval from the molds, or after application of a scratch resistantcoating to the lens.

In a preferred embodiment, the above method may further include theadditional step of directing third activating light rays towards thelens before the oxygen barrier is applied. These third activating lightrays are preferably applied before the gasket is removed. Preferably,the second and third activating light rays are directed toward the backface of the lens (as stated above, the second and third activating lightrays are preferably applied while this lens is in the mold cavity). Thethird activating light rays are preferably about the same range ofintensity as the second activating light rays. The same apparatus may beused for both the second and third activating light rays.

In a preferred embodiment, the method described above also includes thestep of removing the oxygen barrier from the edges of the lens.

The second and third activating light rays may be repeatedly directedtowards the lens. For instance, these activating light rays may beapplied via a light assembly whereby the lens passes under a lightsource on a movable stand. The lens may be repeatedly passed under thelights. Repeated exposure of the lens to the activating light rays maybe more beneficial than one prolonged exposure.

Preferably the oxygen barrier includes a film, and more preferably aplastic, flexible, and/or elastic film. In addition, the oxygen barrieris preferably at least partially transparent to activating, light sothat activating light may penetrate the oxygen barrier to cure anyremaining liquid lens forming composition. Preferably, the oxygenbarrier is stretchable and self-sealing. These features make the filmeasier to apply. Preferably, the oxygen barrier is resistant topenetration by liquids, thus keeping any liquid lens forming compositionin the mold assembly. Preferably, the oxygen barrier includes athermoplastic composition. It is anticipated that many different oxygenbarriers may be used (e.g., saran wrap, polyethylene, etc.). In onepreferred embodiment, the film is “Parafilm M Laboratory Film” which isavailable from American National Can (Greenwich, Conn., U.S.A.). Theoxygen barrier may also include aluminum foil.

Preferably, the oxygen barrier is less than about 1.0 mm thick. Morepreferably, the oxygen barrier is 0.01 to 0.10 mm thick, and morepreferably still, the oxygen barrier is less than 0.025 mm thick. If theoxygen barrier is too thick, then it may not be readily stretchableand/or conformable, and it may not allow a sufficient amount of light topass through it. If the oxygen barrier is too thin, then it may tend totear.

In an alternate method, a lens may be cured between two mold members.The gasket may be removed and any remaining liquid lens composition maybe removed. At this point a mold member may be applied to asubstantially solid conductive heat source. Heat may then beconductively applied to a face of the lens by (a) conductivelytransferring heat to a face of a mold member from the conductive heatsource, and (b) conductively transferring heat through such mold memberto the face of the lens. The oxygen barrier enriched with photoinitiatormay then be applied, and second activating light rays may be directedtowards the lens to cure the remaining lens forming composition.

4. Applying Coating Materials to Lenses

In an embodiment, coating apparatus 20 may be used to apply a pre-coatto a lens before the hardcoat is applied. The pre-coat may serve toincrease the “wettability” of the surface to which the hardcoat is to beapplied. A surfactant has been conventionally employed for this purpose,however surfactants tend to affect the volatility and flowcharacteristics of lens coatings in an unfavorable manner. The pre-coatmay include acetone and/or BYK-300. Upon even distribution of thehardcoat onto a lens, the coating may be wiped near the edges of thelens to prevent the formation of excessive flakes during curing.

5. Curing by the Application of Pulsed Activating Light

A polymerizable lens forming composition may be placed in a mold/gasketassembly and continuously exposed to appropriate levels of activatinglight to cure the composition to an optical lens. The progress of thecuring reaction may be determined by monitoring the internal temperatureof the composition. The lens forming composition may be considered topass through three stages as it is cured: (1) induction, (2) gelformation & exotherm, and (3) extinction. These stages are illustratedin FIG. 22 for a −0.75-1.00 power lens cured by continuous applicationof activating light. FIG. 22 shows temperature within the mold cavity asa function of time throughout a continuous radiation curing cycle.

The induction stage occurs at the beginning of the curing cycle and istypically characterized by a substantially steady temperature of thelens forming composition as it is irradiated with activating light (orfalling temperature when the curing chamber temperature is below that ofthe composition). During the induction period, the lens formingcomposition remains in a liquid state as the photoinitiator breaks downand consumes inhibitor and dissolved oxygen present in the composition.As the inhibitor content and oxygen content of the composition fall,decomposing photoinitiator and the composition begin to form chains toproduce a pourable, “syrup-like” material.

As irradiation continues, the “syrup” proceeds to develop into a soft,non-pourable, viscous, gel. A noticeable quantity of heat will begin tobe generated during this soft gel stage. The optical quality of the lensmay be affected at this point. Should there be any sharp discontinuitiesin the intensity of the activating light (for example, a drop ofcomposition on the exterior of a mold which focuses light into a portionof the lens forming composition proximate the drop), a local distortionwill tend to be created in the gel structure, likely causing anaberration in the final product. The lens forming composition will passthrough this very soft gel state and through a firm gel state to becomea crystalline structure. When using OMB-91 lens forming composition, ahaze tends to form momentarily during the transition between the gel andcrystalline stages. As the reaction continues and more double bonds areconsumed, the rate of reaction and the rate of heat generated by thereaction will slow, which may cause the internal temperature of the lensforming composition to pass through a maximum at the point where therate of heat generation exactly matches the heat removal capacity of thesystem.

By the time the maximum temperature has been reached and the lensforming composition begins to cool, the lens will typically haveachieved a crystalline form and will tend to crack rather than crumbleif it is broken. The rate of conversion will slow dramatically and thelens may begin to cool even though some reaction still may be occurring.Irradiation may still be applied through this extinction phase.Generally, the curing cycle is assumed to be complete when thetemperature of the lens forming composition falls to a temperature nearits temperature at the beginning of exotherm (i.e., the point where thetemperature of the composition increased due to the heat released by thereaction).

The continuous irradiation method tends to work well for relatively lowmass lenses (up to about 20-25 grams, see, e.g., U.S. Pat. Nos.5,364,256 and 5,415,816). As the amount of material being curedincreases, problems may be encountered. The total amount of heatgenerated during the exothermic phase is substantially proportional tothe mass of the lens forming material. During curing of relatively highmass lenses, a greater amount of heat is generated per a given time thanduring curing of lower mass lenses. The total mold/gasket surface areaavailable for heat transfer (e.g., heat removal from the lens formingcomposition), however, remains substantially constant. Thus, theinternal temperature of a relatively high mass of lens forming materialmay rise to a higher temperature more rapidly than typically occurs witha lower mass of lens forming material. For example, the internaltemperature of a low minus cast-to-finish lens typically will not exceedabout 100° F., whereas certain thicker semi-finished lens “blanks” mayattain temperatures greater than about 350° F. when continually exposedto radiation. The lens forming material tends to shrink as curingproceeds and the release of excessive heat during curing tends to reducethe adhesion between the mold and the lens forming material. Thesefactors may lead to persistent problems of premature release and/orcracking during the curing of lens forming material having a relativelyhigh mass.

An advantage of the present method is the production of relativelyhigh-mass, semi-finished lens blanks and high power cast-to-finishlenses without the above-mentioned problems of premature release andcracking. The methods described below allow even more control over theprocess of curing ophthalmic lenses with activating light-initiatedpolymerization than previous methods. By interrupting or decreasing theactivating light at the proper time during the cycle, the rate of heatgeneration and release may be controlled and the incidence of prematurerelease may be reduced. An embodiment relates to a method of controllingthe rate of reaction (and therefore the rate of heat generation) of anactivating light-curable, lens forming material by applying selectedintermittent doses (e.g., pulses) of radiation followed by selectedperiods of decreased activating light or “darkness”. It is to beunderstood that in the description that follows, “darkness” refers tothe absence of activating radiation, and not necessarily the absence ofvisible light.

More particularly, an embodiment relates to: (a) an initial exposureperiod of the lens forming material to radiation (e.g., continuous orpulsed radiation) extending through the induction period, (b)interrupting or decreasing the irradiation before the material reaches afirst temperature (e.g., the maximum temperature the composition couldreach if irradiation were continued) and allowing the reaction toproceed to a second temperature lower than the first temperature, and(c) applying a sufficient number of alternating periods of exposure anddecreased activating light or darkness to the lens forming material tocomplete the cure while controlling the rate of heat generation and/ordissipation via manipulation of the timing and duration of theradiation, or the cooling in the curing chamber. FIG. 23 shows thetemperature within the mold cavity as a function of time for both (a)continuous activating light exposure and (b) pulsed activating lightexposure.

In the context of this application, a “gel” occurs when the liquid lensforming composition is cured to the extent that it becomes substantiallynon-pourable, yet is still substantially deformable and substantiallynot crystallized.

In the following description, it is to be understood that the term“first period” refers to the length of time of the initial exposureperiod where radiation (e.g., in pulses) is applied to the lens formingcomposition, preferably to form at least a portion of the compositioninto a gel. “First activating” rays or light refers to the radiationapplied to the lens forming composition during the initial exposureperiod. “Second activating” rays or light refers to the radiation thatis applied to the lens forming composition (e.g., in pulses) after thecomposition has been allowed to cool to the “third temperature”mentioned above. “Second period” refers to the duration of time thatsecond activating rays are directed to the lens forming composition.“Third period” refers to the duration of decreased activating light ordarkness that ensues after activating light has been delivered in thesecond period.

In an embodiment, the lens forming material is preferably placed in amold cavity defined in part between a first mold member and a secondmold member. The first mold member and/or second mold member may or maynot be continuously cooled as the formation of the lens is completedduring the second period and/or third period. One method of removingheat from the lens forming material is to continuously direct air at anon-casting face of at least one of the mold members. It is preferredthat air be directed at both the first and second mold members. A coolermay be used to cool the temperature of the air to a temperature belowambient temperature, more preferably between about 0° C. and about 20°C., and more preferably still between about 3° C. and about 15° C. Airmay also be used to cool at least one of the mold members (in any of themanners described previously) during the first period.

In an embodiment, the first period ends when at least a portion of thelens forming composition begins to increase in temperature or form agel, and the first activating rays are decreased or removed (e.g.,blocked) such that they cease to contact the first or second moldmembers. It is preferred that the first period be sufficient to allowthe lens forming material to gel in the mold cavity such that there issubstantially no liquid present (except small amounts proximate the edgeof the material). The interruption of irradiation prior to completegellation may in some circumstances produce optical distortions. It ispreferred that the length of the first period be selected to inhibit thelens forming composition from reaching a first temperature. The firsttemperature is preferably the maximum temperature that the lens formingcomposition could reach if it was irradiated under the system conditions(e.g., flow rate and temperature of any cooling air, wavelength andintensity of radiation) until the “exothermic potential” (i.e., abilityto evolve heat through reaction) of the composition was exhausted.

According to an embodiment, the reactions within the composition arepreferably allowed to proceed after the first activating rays areremoved until the composition reaches a second temperature. The secondtemperature is preferably less than the first temperature. The firsttemperature is preferably never reached by the composition. Thus, thecomposition is preferably prevented from achieving the first temperatureand then cooling to the second temperature. The composition ispreferably allowed to cool from the second temperature to the thirdtemperature. This cooling may occur “inactively” by allowing heat totransfer to the ambient surroundings, or at least one of the moldmembers may be cooled by any of the methods described above.

In an embodiment, the curing of the lens forming material may becompleted by directing second activating rays (e.g., in pulses) towardat least one of the mold members. The second activating rays may bedirected toward the mold member(s) for a second period that may bedetermined according to the rate of reaction of the lens formingcomposition. The change in temperature of the composition or a portionof the mold cavity, or the air in or exiting the chamber may be anindicator of the rate of reaction, and the second period may bedetermined accordingly. The second period may be varied such thatsubsequent pulses have a longer or shorter duration than previouspulses. The time between pulses (i.e., the third period) may also bevaried as a function of the temperature and/or reaction rate of thecomposition. To achieve a light pulse, (a) the power to a light sourcemay be turned on and then off, (b) a device may be used to alternatelytransmit and then block the passage of light to the lens formingcomposition, or (c) the light source and/or mold assembly may be movedto inhibit activating light from contacting the lens forming material.The second and/or third periods are preferably controlled to allow rapidformation of a lens while reducing the incidence of (a) prematurerelease of the lens from the first and/or second mold member and/or (b)cracking of the lens.

In an embodiment, the second period is preferably controlled to inhibitthe temperature of the composition from exceeding the secondtemperature. The temperature of the lens forming composition maycontinue to increase after radiation is removed from the first and/orsecond mold members due to the exothermic nature of reactions occurringwithin the composition. The second period may be sufficiently brief suchthat the pulse of second activating rays is removed while thetemperature of the composition is below the second temperature, and thetemperature of the composition increases during the third period tobecome substantially equal to the second temperature at the point thatthe temperature of the composition begins to decrease.

In an embodiment, the third period extends until the temperature of thecomposition becomes substantially equal to the third temperature. Oncethe temperature of the composition decreases to the third temperature, apulse of second activating rays may be delivered to the composition. Inan embodiment, the second period remains constant, and the third periodis preferably controlled to maintain the temperature of the compositionbelow the second temperature. The third period may be used to lower thetemperature of the composition to a temperature that is expected tocause the composition to reach but not exceed the second temperatureafter a pulse is delivered to the composition.

In an embodiment, a shutter system may be used to control theapplication of first and/or second activating rays to the lens formingmaterial. The shutter system preferably includes air-actuated shutterplates that may be inserted into the curing chamber to preventactivating light from reaching the lens forming material. Alternatively,the shutter system may include an LCD panel. Controller 50 may receivesignals from thermocouple(s) located inside the lens-curing chamber,proximate at least a portion the mold cavity, or located to sense thetemperature of air in or exiting the chamber, allowing the timeintervals in which the shutters are inserted and/or extracted to beadjusted as a function of a temperature within the curing chamber. Thethermocouple may be located at numerous positions proximate the moldcavity and/or casting chamber.

The wavelength and intensity of the second activating rays arepreferably substantially equal to those of the first activating rays. Itmay be desirable to vary the intensity and/or wavelength of theradiation (e.g., first or second activating rays). The particularwavelength and intensity of the radiation employed may vary amongembodiments according to such factors as the identity of the compositionand curing cycle variables.

Numerous curing cycles may be designed and employed. The design of anoptimal cycle should include consideration of a number of interactingvariables. Significant independent variables include: 1) the mass of thesample of lens forming material, 2) the intensity of the light appliedto the material, 3) the physical characteristics of the lens formingmaterial, and 4) the cooling efficiency of the system. Significantcuring cycle (dependent) variables include: 1) the optimum initialexposure time for induction and gelling, 2) the total cycle time, 3) thetime period between pulses, 4) the duration of the pulses, and 5) thetotal exposure time.

Most of the experiments involving these methods were conducted usingbelow described OMB-91 monomer. The OMB-91 formulation and propertiesare listed below.

OMB-91 FORMULATION INGREDIENT WEIGHT PERCENT Sartomer SR 351(Trimethylolpropane  20.0 +/− 1.0 Triacrylate) Sartomer SR 268(Tetraethylene Glycol  21.0 +/− 1.0 Diacrylate) Sartomer SR 306(Tripropylene Glycol  32.0 +/− 1.0 Diacrylate) Sartomer SR 239 (1,6Hexanediol  10.0 +/− 1.0 Dimethacrylate) (Bisphenol A Bis(AllylCarbonate))  17.0 +/− 1.0 Irgacure 184 (1-Hydroxycyclohexyl Phenyl 0.017+/− 0.0002 Ketone) Methyl Benzoyl Formate 0.068 +/− 0.0007 Methyl Esterof Hydroquinone (“MeHQ”)   35 ppm +/− 10 ppm Thermoplast Blue P(9,10-Anthracenedione, 0.35 ppm +/− 0.1 ppm 1-hydroxy-4-((4-methylphenyl) Amino) PROPERTY PROPOSED SPECIFICATION MEASUREMENTS/PROPERTIES:Appearance Clear Liquid Color (APHA) 50 maximum (Test Tube Test) MatchStandard Acidity (ppm as Acrylic Acid) 100 maximum Refractive Index1.4725 +/− 0.002 Density  1.08 +/− 0.005 gm/cc. at 23 ° C. Viscosity @22.5 Degrees C  27.0 +/− 2 centipoise Solvent Weight (wt %)   0.1Maximum Water (wt %)   0.1 Maximum MeHQ (from HPLC) 35 ppm +/− 10 ppm

It should be recognized that methods and systems disclosed could beapplied to a large variety of radiation-curable, lens forming materialsin addition to those mentioned herein. It should be understood thatadjustments to curing cycle variables (particularly the initial exposuretime) may be required even among lens forming compositions of the sametype due to variations in inhibitor levels among batches of the lensforming compositions. In addition, changes in the heat removal capacityof the system may require adjustments to the curing cycle variables(e.g. duration of the cooling periods between radiation pulses). Changesin the cooling capacity of the system and/or changes in compositions ofthe lens forming material may require adjustments to curing cyclevariables as well.

Significant variables impacting the design of a pulsed curing cycleinclude (a) the mass of the material to be cured and (b) the intensityof the activating light applied to the material. If a sample isinitially overdosed with radiation, the reaction may progress too farand increase the likelihood of premature release and/or cracking. If asample is underdosed initially in a fixed (i.e., preset) curing cycle,subsequent exposures may cause too great a temperature rise later in thecycle, tending to cause premature release and/or cracking. Additionally,if the light intensity varies more than about +/−10% in a cycle that hasbeen designed for a fixed light intensity level and/or fixed mass oflens forming material, premature release and/or cracking may result.

An embodiment involves a curing cycle having two processes. A firstprocess relates to forming a dry gel by continuously irradiating a lensforming composition for a relatively long period. The material ispreferably cooled down to a lower temperature under darkness, after theirradiation is complete. A second process relates to controllablydischarging the remaining exothermic potential of the material byalternately exposing the material to relatively short periods ofirradiation and longer periods of decreased irradiation (e.g., darkcooling).

The behavior of the lens forming material during the second process willdepend upon the degree of reaction of the lens forming material that hasoccurred during the first process. For a fixed curing cycle, it ispreferable that the extent of reaction occurring in the first processconsistently fall within a specified range. If the progress of reactionis not controlled well, the incidence of cracking and/or prematurerelease may rise. For a curing cycle involving a composition having aconstant level of inhibitor and initiator, the intensity of theradiation employed is the most likely source of variability in the levelof cure attained in the first process. Generally, a fluctuation of +/−5%in the intensity tends to cause observable differences in the cure levelachieved in the first process. Light intensity variations of +/−10% maysignificantly reduce yield rates.

The effect of various light intensities on the material being cureddepends upon whether the intensity is higher or lower than a preferredintensity for which the curing cycle was designed. FIG. 25 showstemperature profiles for three embodiments in-which different lightlevels were employed. If the light intensity to which the material isexposed is higher than a preferred intensity, the overdosage may causethe reaction to proceed too far. In such a case, excessive heat may begenerated, increasing the possibility of cracking and/or prematurerelease during the first process of the curing cycle. If prematurerelease or cracking of the overdosed material does not occur in thefirst process, then subsequent pulses administered during the secondprocess may create very little additional reaction.

If the light intensity is lower than a preferred intensity and the lensforming material is underdosed, other problems may arise. The materialmay not be driven to a sufficient level of cure in the first process.Pulses applied during the second process may then cause relatively highamounts of reaction to occur, and the heat generated by reaction may bemuch greater than the heat removal capacity of the system. Thus thetemperature of the lens forming material may tend to excessivelyincrease. Premature release may result. Otherwise, undercured lensesthat continue generating heat after the end of the cycle may beproduced.

The optimal initial radiation dose to apply to the lens forming materialmay depend primarily upon its mass. The initial dose may also be afunction of the light intensity and exposure time. A method fordesigning a curing cycle for a given mold/gasket/monomer combination mayinvolve selecting a fixed light intensity.

The methods disclosed may involve a wide range of light intensities.Using a relatively low intensity may allow for the length of eachcooling step to be decreased such that shorter and more controllablepulses are applied. Where a fluorescent lamp is employed, the use of alower intensity may allow the use of lower power settings, therebyreducing the load on the lamp cooling system and extending the life ofthe lamp. A disadvantage of using a relatively low light intensity isthat the initial exposure period may be somewhat longer. Relatively highintensity levels tend to provide shorter initial exposure times whileplacing more demand upon the lamp drivers and/or lamp cooling system,either of which tends to reduce the life of the lamp.

Once a light intensity is selected, the initial exposure time may bedetermined. A convenient method of monitoring the reaction during thecycle involves fashioning a fine gauge thermocouple, positioning itinside the mold cavity, and connecting it to an appropriate dataacquisition system. A preferred thermocouple is Type J, 0.005 inchdiameter, Teflon-insulated wire available from Omega Engineering. Theinsulation is preferably stripped back about 30 to 50 mm and each wireis passed through the gasket wall via a fine bore hypodermic needle. Theneedle is preferably removed and the two wires may be twisted togetherto form a thermocouple junction inside the inner circumference of thegasket. The other ends of the leads may be attached to a miniatureconnector which may be plugged into a permanent thermocouple extensioncord leading to the data acquisition unit after the mold set is filled.

The data acquisition unit may be a Hydra 2625A Data Logger made by JohnFluke Mfg. Company. It is preferably connected to an IBM compatiblepersonal computer running Hydra Data Logger software. The computer ispreferably configured to display a trend plot as well as numerictemperature readings on a monitor. The scan interval may be set to anyconvenient time period and a period of five or ten seconds usuallyprovides good resolution.

The position of the thermocouple junction in the mold cavity may affectits reading and behavior through the cycle. When the junction is locatedbetween the front and back molds, relatively high temperatures may beobserved compared to the temperatures at or near the mold face. Thedistance from the edge of the cavity to the junction may affect bothabsolute temperature readings as well as the shape of the curing cycle'stemperature plot. The edges of the lens forming material may begin toincrease in temperature slightly later than other portions of thematerial. Later in the cycle, the lens forming material at the centermay be somewhat ahead of the material at the edge and will tend torespond little to the radiation pulses, whereas the material near theedge may tend to exhibit significant activity. When performingexperiments to develop curing cycles, it is preferred to insert twoprobes into the mold cavity, one near the center and one near the edge.The center probe should be relied upon early in the cycle and the edgeprobe should guide the later stages of the cycle.

Differing rates of reaction among various regions of the lens formingmaterial may be achieved by applying a differential light distributionacross the mold face(s). Tests have been performed where “minus type”light distributions have caused the edge of the lens forming material tobegin reacting before the center of the material. The potentialadvantages of using light distributing filters to cure high masssemi-finished lenses may be offset by non-uniformity of total lighttransmission that tends to occur across large numbers of filters.

After the selection and/or configuration of (a) the radiation intensity,(b) the radiation-curable, lens forming material, (c) the mold/gasketset, and (d) the data acquisition system, the optimum initial exposureperiod may be determined. It is useful to expose a sample of lensforming material to continuous radiation to obtain a temperatureprofile. This will provide an identifiable range of elapsed time withinwhich the optimal initial exposure time will fall. Two points ofinterest may be the time where the temperature rise in the sample isfirst detected (“T initial” or “Ti”), and the time where the maximumtemperature of the sample is reached (“Tmax”). Also of interest is theactual maximum temperature, an indication of the “heat potential” of thesample under the system conditions (e.g., in the presence of cooling).

As a general rule, the temperature of high mass lenses (i.e., lensesgreater than about 70 grams) should remain under about 200° F. andpreferably between about 150° F. and about 180° F. Higher temperaturesare typically associated with reduced lens yield rates due to crackingand/or premature release. Generally, the lower mass lenses (i.e., lensesno greater than about 45 grams) should be kept under about 150° F. andpreferably between about 110° F. and about 140° F.

The first period may be selected according to the mass of the lensforming material. In an embodiment, the lens forming material has a massof between about 45 grams and about 70 grams and a selected secondtemperature between about 150° F. and about 200° F. According to anotherembodiment, the lens forming material has a mass no greater than about45 grams and a second temperature less than about 150° F. In yet anotherembodiment, the lens forming material has a mass of at least about 70grams, and a second temperature between about 170° F. and about 190° F.

An experiment may be performed in which the radiation is removed fromthe mold members slightly before one-half of the time between T initialand Tmax. The initial exposure time may be interactively reduced orincreased according to the results of the above experiment in subsequentexperiments to provide a Tmax in a preferred range. This procedure mayallow the determination of the optimal initial exposure time for anygiven mold/gasket set and light intensity.

A qualitative summary of relationships among system variables related tothe above-described methods is shown in FIG. 24.

After the initial exposure period, a series of irradiation pulse/coolingsteps may be performed to controllably discharge the remainingexothermic potential of the material and thus complete the cure. Theremay be at least two approaches to accomplish this second process. Thefirst involves applying a large number of very short pulses and shortcooling periods. The second approach involves applying a fewer number oflonger pulses with correspondingly longer cooling periods. Either ofthese two methods may produce a good product and many acceptable cyclesmay exist between these extremes.

The described method relates to using pulsed application of light toproduce a large range (e.g., from −6 to +4 diopter) of lenses withoutrequiring refrigerated cooling fluid (e.g., cooled air). With properlight application, air at ambient may be used as a cooling fluid, thussignificantly reducing system costs.

The following general rules for the design of pulse/cooling cycles maybe employed to allow rapid curing of a lens while inhibiting prematurerelease and/or cracking of the lens. The duration of the pulsespreferably does not result in a temperature that exceeds the maximumtemperature attained in the initial exposure period. The length of thecooling period may be determined by the length of time necessary for theinternal temperature of the lens forming material to return to near thetemperature it had immediately before it received a pulse. Followingthese general rules during routine experimentation may permit propercuring cycles to be established for a broad range of lens formingmaterials, light intensity levels, and cooling conditions.

Preferably, light output is measured and controlled by varying theamount of power applied to the lights in response to changes in lightoutput. Specifically, a preferred embodiment includes a light sensormounted near the lights. This light sensor measures the amount of light,and then a controller increases the power supplied to maintain the firstactivating light rays as the intensity of the first activating lightrays decreases during use, and vice versa. Preferably, the power isvaried by varying the electric frequency supplied to the lights.

In an embodiment, a medium pressure mercury vapor lamp is used to curethe lens forming material and the lens coating. This lamp and manyconventional light sources used for activating light curing may not berepeatedly turned on and off since a several minute warm-up period isgenerally required prior to operation. Mercury vapor light sources maybe idled at a lower power setting between exposure periods (i.e., secondperiods), however, the light source will still generate significant heatand consume electricity while at the lower power setting.

In an embodiment, air at ambient temperature may be used to cool thelens forming composition. When a xenon flash lamp is used, the pulses oflight generally have a duration of much less than about one second andconsiderably less radiative heat tends to be transferred to the lensforming composition compared to curing methods employing otheractivating light sources. Thus, the reduced heat imparted to the lensforming composition may allow for air at ambient temperature to removesufficient heat of exotherm to substantially inhibit premature releaseand/or cracking of the lens.

In an embodiment, a xenon source is used to direct first activatinglight rays toward the first and second mold members to the point that atemperature increase is measured and/or the lens forming compositionbegins to or forms a gel. It is preferred that the gel is formed withless than 15 pulses of radiation, and more preferably with less thanabout 5 pulses. It is preferred that the gel is formed before the totaltime to which the composition has been exposed to the pulses exceedsabout {fraction (1/10)} or {fraction (1/100)} of a second.

In an embodiment, a reflecting device is preferably employed inconjunction with the xenon light source. The reflecting device ispositioned behind the flash source and preferably allows an evendistribution of activating light rays from the center of the compositionto the edge of the composition.

In an embodiment, a xenon light flash lamp is preferably used to apply aplurality of activating light pulses to the lens forming composition tocure it to an eyeglass lens in a time period of less than 30 minutes, ormore preferably, less than 20 or 15 minutes.

The use of a xenon light source also may allow the formation of lensesover a wider range of diopters. Higher power lenses exhibit greatestthinnest to thickest region ratios, meaning that more shrinkage-inducedstress may be created, causing greater mold flexure and thus increasedtendency for premature release. Higher power lenses also possess thickerregions. Portions of lens forming material within these thicker regionsmay receive less light than regions closer to the mold surfaces.Continuous irradiation lens forming techniques typically require the useof relatively low light intensities to control the heat generated duringcuring. The relatively low light intensities used tends to result in along, slow gellation period. Optical distortions tend to be created whenone portion of the lens is cured at a different rate than anotherportion. Methods characterized by non-uniform curing are typicallypoorly suited for the production of relatively high power lenses, sincethe deeper regions (e.g., regions within a thick portion of a lens) tendto gel at a slower rate than regions closer to the mold surfaces.

The relatively high intensity attainable with the xenon source may allowdeeper penetration into, and/or saturation of, the lens formingmaterial, thereby allowing uniform curing of thicker lenses than inconventional radiation-initiated curing. More uniform gelation may occurwhen the lens forming material is dosed with a high intensity pulse ofactivating light and then subjected to decreased activating light ordarkness as the reaction proceeds without activating radiation. Lenseshaving a diopter of between about +5.0 and about −6.0 and greater may becured. It is believed that light distribution across the sample is lesscritical when curing and especially when gelation is induced withrelatively high intensity light. The lens forming material may becapable of absorbing an amount of energy per time that is below thatdelivered during a relatively high intensity pulse. The lens formingmaterial may be “oversaturated” with respect to the light delivered viaa high intensity flash source. In an embodiment, the xenon source ispreferably used to cure a lens having a diopter between about −4.0 andabout −6.0. In an embodiment, the xenon source is preferably used tocure a lens having a diopter between about +2.0 and about +4.0.

The methods disclosed herein allow curing of high-mass semi-finishedlens blanks from the same material used to cure cast-to-finish lenses.Both are considered to be “eyeglass lenses” for the purposes of thispatent. These methods may also be used to cure a variety of other lensforming materials. These methods have been successfully used to makecast-to-finish lenses in addition to semi-finished lenses.

6. Improved Lens Curing Process

When casting an eyeglass lens with activating light, the gelationpattern of the lens forming composition may affect the resultant opticalquality of the lens. If there are localized discontinuities in the lightintensities received by the monomer contained in the casting cavityduring the early stages of the polymerization process, opticaldistortions may be seen in the finished product. Higher power lensesare, by definition, thicker in certain regions than relatively lowerpower lenses of the same diameter. The layers of a lens closest to themold faces of the casting cavity tend to receive a higher lightintensity than the deeper layers because the lens forming compositionabsorbs some of the incident light. This causes the onset ofpolymerization to be delayed in the deeper layers relative to the outerlayers, which may cause optical distortions in the finished product. Itis believed that concurrent with this differential curing rate, there isa difference in the rate of exothermic heat generation, specifically,the deeper regions will begin to generate heat after the outer regionsin the cavity have already cured and the effectiveness of the heatremoval may be impaired, contributing to optical waves and distortionsin the finished product. This phenomena is particularly observable inhigh powered positive lenses due to the magnification of such defects.

In an embodiment, the lens forming composition contained within thecasting cavity is exposed to relatively high intensity activating lightfor a time period sufficient to initialize the reaction. Irradiation ispreferably terminated before the polymerization of the lens formingcomposition proceeds far enough to generate a substantial amount ofheat. This initial relatively high intensity dose preferablysubstantially uniformly gels the material within the casting cavity suchthat the difference in the rate of reaction between the inner and outerlayers of the lens being cured is preferably reduced, therebyeliminating the waves and distortions often encountered when usingcontinuous low intensity irradiation to initialize the reaction,particularly with high dioptric power positive lenses.

In an embodiment, the relatively high intensity dose of activating lightis preferably applied to the lens forming composition in the form ofpulses. The pulses preferably have a duration of less than about 10seconds, preferably less than about 5 seconds, and more preferably lessthan about 3 seconds. The pulses preferably have an intensity of atleast about 10 milliwatts/cm², more preferably at least about 100milliwatts/cm², and more preferably still between about 150milliwatts/cm² and about 250 milliwatts/cm². It is preferred thatsubstantially all of the lens forming composition forms into a gel afterthe initial application of the relatively high intensity activatinglight. In an embodiment, no more than an insubstantial amount of heat isgenerated by exothermic reaction of the lens forming composition duringthe initial application of the relatively high intensity activatinglight.

Subsequent to this initial high intensity dose, a second irradiationstep may be performed in which the material contained within the castingcell is preferably irradiated for a relatively longer time at arelatively lower intensity while cool fluid is directed at thenon-casting surface of at least one of the molds forming the cavity. Thecooling fluid preferably removes the exothermic heat generated by thepolymerization of the lens forming composition. If the intensity of theactivating light is too great during this second irradiation step, therate of heat generation will tend to be too rapid and the lens mayrelease prematurely from the casting face of the mold and/or crack.Similarly, should the rate of heat removal from the lens formingcomposition be too slow, the lens may release prematurely and/or crack.It is preferred that the mold/gasket assembly containing the lensforming composition be placed within the cooling environment as shortlyafter the initial dose of activating light as possible.

In an embodiment, the activating light applied to the lens formingcomposition during the second irradiation step is preferably less thanabout 350 microwatts/cm², more preferably less than about 150microwatts/cm², and more preferably still between about 90microwatts/cm² and about 100 microwatts/cm². During the secondirradiation step, the activating light may be applied to the lensforming composition continuously or in pulses. A translucent highdensity polyethylene plate may be positioned between the activatinglight generator and at least one of the mold members to reduce theintensity of the activating light to within a preferred range.

In an embodiment, relatively high intensity activating light ispreferably applied to the lens curing composition in a third irradiationstep to post-cure the lens subsequent to the second relatively lowintensity irradiation step. In the third irradiation step, pulses ofactivating light are preferably directed toward the lens formingcomposition, although the composition may be continuously irradiatedinstead. The pulses preferably have an intensity of at least about 10milliwatts/cm², more preferably at least about 100 milliwatts/cm², andmore preferably still between about 100 milliwatts/cm² and about 150milliwatts/cm².

Each of the above-mentioned irradiation steps is preferably performed bydirecting the activating light through each of the first and second moldmembers. The eyeglass lens is preferably cured in a total time of lessthan 30 minutes and is preferably free of cracks, striations,distortions, haziness, and yellowness.

It is believed that the above-described methods enable the production ofwhole lenses in prescription ranges beyond those currently attainablewith continuous low intensity irradiation. The method may be practicedin the curing of relatively high or low power lenses with a reducedincidence of optical distortions in the finished lens as compared toconventional methods. It is to be understood that the above-describedmethods may be used independently or combined with the methods andapparatus of preferred embodiments described above in the previoussections.

7. Improved Scratch Resistant Lens Formation Process

The “in-mold” method involves forming a scratch resistant coating overan eyeglass lens by placing the liquid coating in a mold andsubsequently curing it. The in-mold method may be advantageous to“out-of-mold” methods since the in-mold method exhibits less occurrencesof coating defects manifested as irregularities on the anterior surfaceof the coating. Using the in-mold method produces a scratch resistantcoating that replicates the topography and smoothness of the moldcasting face. However, a problem encountered when using conventionalin-mold scratch resistant coatings is that minute “pinholes” often formin the coating. It is believed that the pinholes may be caused by eithercontaminants on the mold, airborne particles falling on the coatingbefore it is cured, or bubbles formed during the application of thecoating which burst afterwards. The formation of such pinholes isespecially prevalent when using a flat-top bifocal mold, such as the onedepicted in FIG. 29. As illustrated, the segment line 454 of a bifocalsegment 452 below the main surface 456 of the mold reduces thesmoothness of the casting face. When a coating is spin-coated over themold face, this indentation may become an obstacle to the even flow ofthe casting face. The pinhole defects may be a problem in tinted lensesbecause the dye used to tint a lens may penetrate through the pinholes,resulting in a tiny speck of dye visible in the lens.

According to an embodiment, a first coating composition (i.e., apolymerizable “prime” material) is preferably passed through a filterand then placed within a mold member having a casting face and anon-casting face. The first coating composition preferably contains aphotoinitiator to make it curable upon exposure to activating light. Themold member may then be spun so that the first composition becomesdistributed over the casting face. The mold member may be rotated abouta substantially vertical axis at a speed between about 750 and about1500 revolutions per minute, preferably between about 800 and about 1000revolutions per minute, more preferably at about 900 revolutions perminute. Further, a dispensing device may be used to direct an additionalamount of the first composition onto the casting face while the moldmember is spinning. The dispensing device preferably moves from thecenter of the mold member to an edge of the mold member so that theadditional amount is preferably directed along a radius of the moldmember. Activating light is preferably directed at the mold member tocure at least a portion of the first composition.

A second coating composition may then be placed upon the firstcomposition in the mold member. The second coating is also preferablycurable when exposed to activating light because it contains aphotoinitiator. The mold member is preferably spun to distribute thesecond coating composition over the cured portion of the first coatingcomposition. The mold member may also be spun simultaneously whileadding the second composition to the mold member. Activating light isthen preferably directed at the mold member to simultaneously cure atleast a portion of the second coating composition and form a transparentcombination coat having both coating compositions. The combination coatis preferably a substantially scratch-resistant coating. The mold membermay then be assembled with a second mold member by positioning a gasketbetween the members to seal them. Therefore, a mold having a cavityshared by the original two mold members is formed. An edge of the gasketmay be displaced to insert a lens-forming composition into the cavity.The combination coat and the lens-forming material preferably adherewell to each other. This lens-forming composition preferably comprises aphotoinitiator and is preferably cured using activating light. Air whichpreferably has a temperature below ambient temperature may be directedtoward a non-casting face of the second mold member to cool thelens-forming composition while it is being cured.

The primer coat preferably comprises a mixture of high viscositymonomers, a low viscosity, low flashpoint organic solvent, and asuitable photoinitiator system. The solvent may make up more than about80% of the mixture, preferably about 93% to 96%. This mixture preferablyhas low viscosity and preferably covers any surface irregularity duringthe spin application, for example the segment line of a flat-top bifocalmold. The low flashpoint solvent preferably evaporates off relativelyquickly, leaving a thin layer of high viscosity monomer, containingphotoinitiator, which coats the casting face of the mold. The curedprimer coat is preferably soft to allow it to adhere well to the glassmold face. Since the primer coat is soft, it may not possess scratchresistant characteristics. However, applying a high scratch resistancehard coating (i.e., the second coating composition) to the primer coatpreferably results in a scratch resistant combination coat. The hardcoat preferably contains a solvent which evaporates when the mold memberis rotated to distribute the hard coating over the primer coat.

In general, the ideal primer material preferably possesses the followingcharacteristics: exhibits chemical stability at normal storageconditions (e.g., at room temperature and in the absence of activatinglight); flows well on an irregular surface, especially over a flat-topbifocal segment; when cured with a specified activating light dose,leaves a crack-free coating, with a high double bond conversion(approximately greater than 80%); maintains adhesion with the mold facethrough the lens forming curing cycle, especially the segment part ofthe flat-top bifocal mold; and is chemically compatible with the hardcoat that is subsequently applied on top of it (e.g., forms an opticallyclear combination coat). Even though pinhole defects may be present ineither the primer coat or the hard coat, it is highly unlikely thatdefects in one coat would coincide with defects of another coat. Eachcoat preferably covers the holes of the other coat, resulting in lesspinholes in the combination coat. Thus, the finished in-mold coated lensmay be tinted using dye without problems created by pinholes. It is alsopreferably free of cracks, yellowness, haziness, and distortions.

In an embodiment, the gasket between the first mold member and thesecond mold member may be removed after a portion of the lens-formingmaterial has been cured. The removal of the gasket preferably exposes anedge of the lens. An oxygen barrier having a photoinitiator may beplaced around the exposed edge of the lens, wherein the oxygen barrierphotoinitiator is preferably near an uncured portion of the lens-formingcomposition. Additional activating light rays may then be directedtowards the lens to cause at least a portion of the oxygen barrierphotoinitiator to initiate reaction of the lens-forming material. Theoxygen barrier preferably prevents oxygen from contacting at least aportion of the lens forming composition during exposure of the lens tothe activating rays.

According to one embodiment, a substantially solid conductive heatsource is preferably applied to one of the mold members. Heat may beconductively transferred from the heat source to a face of the moldmember. Further, the heat may be conductively transferred through themold member to the face of the lens.

8. Method for Forming a Plastic Lens Containing Ultraviolet/VisibleLight Absorbing Compounds

Materials (hereinafter referred to as “ultraviolet/visible lightabsorbing compounds”) that absorb various degrees of ultraviolet/visiblelight may be used in an eyeglass lens to inhibit ultraviolet/visiblelight from being transmitted through the Ieyeglass lens. Such aneyeglass lens advantageously inhibits ultraviolet/visible light frombeing transmitted to the eye of a user wearing the lens. Curing of aneyeglass lens using activating light to initiate the polymerization of alens forming composition generally requires that the composition exhibita high degree of activating light transmissibility so that theactivating radiation may penetrate to the deeper regions of the lenscavity. Otherwise the resulting cast lens may possess opticalaberrations and distortions. The cast lens may also contain layers ofcured material in the regions closest to the transparent mold faces,sandwiching inner layers which may be either incompletely cured, gelled,barely gelled, or even liquid. Often, when even small amounts ofultraviolet/visible light absorbing compounds of the types well known inthe art are added to a normally activating light curable lens formingcomposition, substantially the entire amount of lens forming compositioncontained within the lens cavity may remain liquid in the presence ofactivating radiation.

Photochromic pigments which have utility for photochromic eyeglasslenses absorb ultraviolet/visible light strongly and change from anunactivated state to an activated state when exposed toultraviolet/visible light. The presence of photochromic pigments, aswell as other ultraviolet/visible light absorbing compounds within alens forming composition, generally does not permit enough activatingradiation to penetrate into the depths of the lens cavity sufficient tocause photoinitiators to break down and initiate polymerization of thelens forming composition. Thus, it may be difficult to cure a lensforming composition containing ultraviolet/visible light absorbingcompounds using activating light. It is therefore desirable to provide amethod for using activating light to initiate polymerization of aneyeglass lens forming monomer which contains ultraviolet/visible lightabsorbing compounds, in spite of the high activating light absorptioncharacteristics of the ultraviolet/visible light absorbing compounds.Examples of such ultraviolet/visible light absorbing compounds otherthan photochromic pigments are fixed dyes and colorless additives.

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer, an ultraviolet/visible lightabsorbing compound, an photoinitiator, and a co-initiator. Examples ofthese compounds are listed in the section “Lens Forming CompositionsIncluding Ultraviolet/Visible Light Absorbing Materials”. The lensforming composition, in liquid form, is preferably placed in a moldcavity defined by a first mold member and a second mold member. It isbelieved that activating light, which is directed toward the moldmembers to activate the photoinitiator, causes the photoinitiator toform a polymer chain radical. The polymer chain radical preferablyreacts with the co-initiator more readily than with the monomer. Theco-initiator may react with a fragment or an active species of eitherthe photoinitiator or the polymer chain radical to produce a monomerinitiating species in the regions of the lens cavity where the level ofactivating light is either relatively low or not present.

The co-initiator is preferably activated only in the presence of thephotoinitiator. Further, without the co-initiator, the photoinitiatormay exclusively be activated near the surface of the lens formingcomposition but not within the middle portion of the composition.Therefore, using a suitable photoinitiator combined with a co-initiatorpermits polymerization of the lens forming composition to proceedthrough the depths of the lens cavity. A cured, clear, aberration freelens is preferably formed in less than about 30 minutes, more preferablyin less than about 10 minutes. The lens, when exposed toultraviolet/visible light preferably inhibits at least a portion of theultraviolet/visible light from being transmitted through the lens thatis preferably formed. A lens that permits no ultraviolet light frompassing through the lens (at least with respect to certain ultravioletwavelengths) is more preferred.

The identity of the major polymerizable components of the lens formingcomposition tends to affect the optimal curing process. It isanticipated that the identity of the ultraviolet/visible light absorbingcompound present in the monomer or blend of monomers may affect theoptimal photoinitiator/co-initiator system used as well as the optimalcuring process used to initiate polymerization. Also, varying theidentities or the proportions of the monomer(s) in the lens formingcomposition may require adjustments to various production processvariables including, but not limited to, exposure times, exposureintensities, cooling times and temperatures, activating light andthermal postcure procedures and the like. For example, compositionscomprising relatively slow reacting monomers, such as bisphenol A bisallyl carbonate or hexanediol dimethacrylate, or compositions comprisingrelatively higher proportions of such monomers may require either longerexposure times, higher intensities, or both. It is postulated thatincreasing the amount of either fast reacting monomer or the initiatorlevels present in a system will require reduced exposure times, morerigidly controlled light doses, and more efficient exothermic heatremoval.

Exothermic reactions may occur during the curing process of the lensforming composition. The thicker portions of the lens formingcomposition may generate more heat than the thinner portions of thecomposition as a result of the exothermic reactions taking place. It isbelieved that the speed of reaction in the thicker sections is slowerthan in the thinner sections. Thus, in a positive lens a “donut effect”may occur in which the relatively thin outer portion of the lens formingcomposition reaches its fully cured state before the relatively thickinner portion of the lens forming composition. Conversely, in a negativelens the relatively thin inner portion of the lens forming compositionmay reach its fully cured state before the relatively thick outerportion of the lens forming composition.

After the lens forming composition is preferably loaded into a moldassembly, the mold assembly is preferably irradiated with activatinglight at an appropriate intensity and duration. Typically, the intensityand duration of activating light required to produce a lens containingultraviolet/visible light absorbers is preferably significantly higherthan the intensity and duration of light required for formingnon-ultraviolet/visible light absorbing lenses. The mold assembly mayalso require multiple doses for curing. This may require a differentapparatus and/or setup from that used to form non-UV absorbing lenses.

In one embodiment, an apparatus may be capable of forming clear,colored, or photochromic lenses without significantly altering theapparatus. In order to achieve this the lens forming composition willpreferably include ultraviolet/visible light absorbers. By placingultraviolet/visible light absorbers in a clear non-photochromic lensforming composition, a clear lens may be obtained under similarconditions to those used for colored and photochromic lenses. Thus, theaddition of ultraviolet/visible light absorbers to a non-photochromiclens forming composition, allows both photochromic and non-photochromiclens forming compositions to be cured using the same apparatus andsimilar procedures. An added advantage, is that the produced clearlenses provide additional ultraviolet/visible light protection to theuser that may not be present in clear lenses formed withoutultraviolet/visible light absorbers. In this manner, plastic lenses maybe formed which exhibit many of the same properties as glass lenseshowever, the plastic lenses may be produced more rapidly, at lower cost,and have a weight significantly less than their glass counterparts.

9. Actinic Light Initiated Polymerization Ultraviolet/Visible LightAbsorbing Compositions

Curing of an eyeglass lens using activating light to initiate thepolymerization of a lens forming composition generally requires that thecomposition exhibit a high degree of activating light transmissibilityso that the activating light may penetrate to the deeper regions of thelens cavity. Otherwise the resulting cast lens may possess opticalaberrations and distortions. The cast lens may also contain layers ofcured material in the regions closest to the transparent mold faces,sandwiching inner layers which may be either incompletely cured, gelled,barely gelled, or even liquid. Often, when even small amounts ofactivating light absorbing compounds have been added to a normallycurable lens forming composition, substantially the entire amount oflens forming composition contained within the lens cavity may remainliquid in the presence of activating light.

Photochromic pigments that have utility for photochromic eyeglass lensestypically absorb activating light strongly and change from aninactivated state to an activated state when exposed to activatinglight. The presence of photochromic pigments, as well as otheractivating light absorbing compounds within a lens forming composition,generally does not permit enough activating radiation to penetrate intothe depths of the lens cavity sufficient to cause photoinitiators tobreak down and initiate polymerization of the lens forming composition.Examples of such activating light absorbing compounds other thanphotochromic pigments are fixed dyes and colorless additives.

It is therefore difficult to cure a lens forming composition containingactivating light absorbing compounds using activating light. Onesolution to this problem involves the use of a co-initiator. By using aco-initiator, activating light may be used to initiate thepolymerization reaction. It is believed that activating light that isdirected toward the mold members may cause the photoinitiator to form apolymer chain radical. The polymer chain radical preferably reacts withthe co-initiator more readily than with the monomer. The co-initiatormay react with a fragment or an active species of either thephotoinitiator or the polymer chain radical to produce a monomerinitiating species in the regions of the lens cavity where the level ofactivating light is either relatively low or not present. It istherefore desirable to provide a method for polymerizing an eyeglasslens forming composition that contains light absorbing compounds byusing activating light having a wavelength that is not absorbed by thelight absorbing compounds, thus avoiding the need for a co-initiator.

In an embodiment, an ophthalmic eyeglass lens may be made from a lensforming composition comprising a monomer, a light absorbing compound,and a photoinitiator, by irradiation of the lens forming compositionwith activating light. As used herein “activating light” means lightthat may effect a chemical change. Activating light may includeultraviolet light, actinic light, visible light or infrared light.Generally any wavelength of light capable of effecting a chemical changemay be classified as activating. Chemical changes may be manifested in anumber of forms. A chemical change may include, but is not limited to,any chemical reaction which causes a polymerization to take place.Preferably the chemical change causes the formation of a initiatorspecies within the lens forming composition, the initiator species beingcapable of initiating a chemical polymerization reaction.

The lens forming composition, in liquid form, is preferably placed in amold cavity defined by a first mold member and a second mold member. Itis believed that activating light, when directed toward and through themold members to activate the photoinitiator, causes the photoinitiatorto form a polymer chain radical. The polymer chain radical may reactwith a fragment or an active species of either photoinitiator or thepolymer chain radical to produce a monomer initiating species in otherregions of the lens cavity.

The use of activating light of the appropriate wavelength preferablyprevents the lens from darkening during the curing process. Herein,“darkening” means becoming at least partially non-transparent to theincoming activating light such that the activating light may notsignificantly penetrate the lens forming composition. Photochromiccompounds may cause such darkening. Ultraviolet/visible light absorbingcompounds present in the lens forming composition may prevent activatinglight having a wavelength substantially below about 380 nm frompenetrating into the lens forming composition. When treated withactivating light containing light with wavelengths in the ultravioletregion, e.g. light with wavelengths below about 380 nm, theultraviolet/visible light absorbing compounds may darken, preventingfurther ultraviolet activating light from penetrating the lens formingcomposition. The darkening of the lens forming composition may alsoprevent non-ultraviolet activating light from penetrating thecomposition. This darkening effect may prevent activating light of anywavelength from initiating the polymerization reaction throughout thelens forming composition.

When the ultraviolet/visible light absorbing compounds absorb in theultraviolet region, activating light having a wavelength above about 380nm (e.g., actinic light) may be used to prevent the darkening effect.Because the wavelength of the activating light is substantially abovethe wavelength at which the ultraviolet/visible light absorbingcompounds absorb, the darkening effect may be avoided. Additionally,activating light with a wavelength above about 380 nm may be used toinitiate the polymerization of the lens forming material. By the use ofsuch activating light an eyeglass lens containing ultraviolet/visiblelight absorbing compounds may, in some circumstances, be formed withoutthe use of a co-initiator.

In an embodiment, the above-described lens forming composition, wherethe ultraviolet/visible light absorbing compound absorbs, predominantly,ultraviolet light, may be treated with activating light having awavelength above about 380 nm to activate the photoinitiator.Preferably, activating light having a wavelength substantially betweenabout 380 nm to 490 nm is used. By using activating light above about380 nm the darkening effect caused by the ultraviolet/visible lightabsorbing compounds may be avoided. The activating light may penetrateinto the lens forming composition, initiating the polymerizationreaction throughout the composition. A filter which blocks light havinga wavelength that is substantially below about 380 nm may be used toprevent the ultraviolet/visible light absorbing compounds fromdarkening.

The use of activating light permits polymerization of the lens formingcomposition to proceed through the depths of the lens cavity. A cured,clear, aberration free lens is preferably formed in less than about30-60 minutes, more preferably in less than about 20 minutes. As usedherein a “clear lens” means a lens that transmits visible light withoutscattering so that objects beyond the lens may be seen clearly. As usedherein “aberration” means the failure of a lens to producepoint-to-point correspondence between an object and its image. The lens,when exposed to ultraviolet/visible light, preferably inhibits at leasta portion of the ultraviolet/visible light from being transmittedthrough the lens. In this manner the eye may be protected from certainlight. A lens that permits no ultraviolet/visible light from passingthrough the lens (at least with respect to certain wavelengths) is morepreferred.

In an embodiment, the lens forming composition that contains anultraviolet/visible light absorbing compound may be cured with anactivating light. Preferably, the activating light has a wavelengthsubstantially above about 380 nm. The lens forming composition may becured by exposing the composition to activating light multiple times.Alternatively, the lens forming composition may be cured by exposing thecomposition to a plurality of activating light pulses, at least one ofthe pulses having a duration of less than about one second (morepreferably less than about 0.1 seconds, and more preferably between 0.1and 0.001 seconds). Preferably, all activating light directed toward themold members is at a wavelength between about 380 nm to 490 nm. Thepreviously described embodiments which describe various methods andcompositions for forming eyeglass lenses may also be utilized to formthe eyeglass lens hereof, by replacing the ultraviolet light in theseexamples with activating light having a wavelength substantially greaterthan about 380 nm.

In an embodiment, the activating light may be generated from afluorescent lamp. The fluorescent lamp is preferably used to directactivating light rays toward at least one of the mold members. At leastone and preferably two fluorescent light sources, with strong emissionspectra in the 380 to 490 nm region may be used. When two light sourcesare used, they are preferably positioned on opposite sides of the moldcavity. A fluorescent lamp emitting activating light with the describedwavelengths is commercially available from Philips Electronics as modelTLD-15W/03.

Preferably, three or four fluorescent lamps may be positioned to providesubstantially uniform radiation over the entire surface of the moldassembly to be cured. The activating light source may be turned on andoff quickly between exposures. A flasher ballast may be used for thisfunction. A flasher ballast may operate in a standby mode wherein a lowcurrent is supplied to the lamp filaments to keep the filaments warm andthereby reduce the strike time of the lamp. Such a ballast iscommercially available from Magnatek, Inc of Bridgeport, Conn.Alternately, the light source may employ a shutter system to block thelight between doses. This shutter system is preferably controlled by amicro-processor based control system in order to provide the necessarydoses of light. A feedback loop may be used to control the lightintensity so that intensity fluctuations due to environmental variables(e.g. lamp temperature) and lamp aging may be minimized. A light sensormay be incorporated into the control system to minimize variances indose for a given exposure time.

The identity of the major polymerizable components of the lens formingcomposition tends to affect the optimal curing process. It isanticipated that the identity of the light absorbing compound present inthe monomer or blend of monomers may affect the optimal photoinitiatorsystem used as well as the optimal curing process used to initiatepolymerization. Also, varying the identities or the proportions of themonomer(s) in the lens forming composition may require adjustments tovarious production process variables including, but not limited to,exposure times, exposure intensities, cooling times and temperatures,postcure procedures and the like. For example, compositions includingrelatively slow reacting monomers, such as bisphenol A bis allylcarbonate or hexanediol dimethacrylate, or compositions includingrelatively higher proportions of such monomers may require either longerexposure times, higher intensities, or both. It is postulated thatincreasing the amount of either fast reacting monomer or the initiatorlevels present in a system will require reduced exposure times, morerigidly controlled light doses, and more efficient exothermic heatremoval.

Preferably, the monomers selected as components of the lens formingcomposition are capable of dissolving the light absorbing compoundsadded to them. As used herein “dissolving” means being substantiallyhomogeneously mixed. For example, monomers may be selected from a groupincluding polyether (allyl carbonate) monomers, multi-functionalacrylate monomers, and multi-functional methacrylic monomers for use inan ultraviolet/visible light absorbing lens forming composition.

In an embodiment, the mixture of monomers, previously described asPRO-629, may be blended together before addition of other componentsrequired to make the lens forming composition. This blend of monomers ispreferably used as the basis for a lens forming composition to whichultraviolet/visible light absorbing compounds are added.

A polymerization inhibitor may be added to the monomer mixture atrelatively low levels to inhibit polymerization of the monomer atinappropriate times (e.g., during storage). Preferably about 0 to 50 ppmof monomethylether hydroquinone (MEHQ) are added to the monomer mixture.It is also preferred that the acidity of the monomer mixture be as lowas possible. Preferably less than about 100 ppm residual acrylic acidexists in the mixture. It is also preferred that the water content ofthe monomer mixture be relatively low, preferably less than about 0.15percent.

Photoinitiators which have utility in the present method have beendescribed in previous embodiments. Ultraviolet/visible light absorbingcompounds which may be added to a normally ultraviolet/visible lighttransmissible lens forming composition have also been described inprevious embodiments. The quantity of photochromic pigments present inthe lens forming composition is preferably sufficient to provideobservable photochromic effect. The amount of photochromic pigmentspresent in the lens forming composition may widely range from about 1ppm by weight to 1-5% by weight. In preferred compositions, thephotochromic pigments are present in ranges from about 30 ppm to 2000ppm. In the more preferred compositions, the photochromic pigments arepresent in ranges from about 150 ppm to 1000 ppm. The concentration maybe adjusted depending upon the thickness of the lens being produced toobtain optimal visible light absorption characteristics.

In another embodiment co-initiators may be added to the lens formingcomposition. As described previously, such compositions may aid thepolymerization of the lens forming composition by interacting with thephotoinitiator such that the composition polymerizes in a substantiallyuniform manner. It is anticipated that the optimal amount of theinitiators is where the total amount of both initiators are minimizedsubject to the constraint of complete polymerization and production of arigid, aberration free lens. The relative proportions of thephotoinitiator to the co-initiator may be optimized by experimentation.For example, an ultraviolet/visible light absorptive lens formingcomposition that includes a photoinitiator with no co-initiator may becured. If waves and distortions are observed in the resulting lens, aco-initiator may then be added to the lens forming composition byincreasing amounts until a lens having the best optical properties isformed. It is anticipated that excess co-initiator in the lens formingcomposition should be avoided to inhibit problems of too rapidpolymerization, yellowing of the lens, and migration of residual,unreacted co-initiator to the surface of the finished lens.

In an embodiment, hindered amine light stabilizers may be added to thelens forming composition. It is believed that these materials act toreduce the rate of degradation of the cured polymer caused by exposureto ultraviolet light by deactivating harmful polymer radicals. Thesecompounds may be effective in terminating oxygen and carbon freeradicals, and thus interfering with the different stages ofauto-oxidation and photo-degradation. Preferably, more than one monomerand more than one initiator are used in a lens forming composition toensure that the initial polymerization of the lens forming compositionwith activating light does not occur over too short a period of time.The use of such a lens forming composition may allow greater controlover the gel formation, resulting in better control of the opticalquality of the lens.

An eyeglass lens formed using the lens forming compositions describedmay be applicable for use as a prescription lens and for anon-prescription lens. Particularly, such a lens may be used insunglasses. Advantageously, photochromic sunglass lenses would remainlight enough in color to allow a user to see through them clearly whileat the same time prohibiting ultraviolet/visible light from passingthrough the lenses. In one embodiment, a background dye may be added tothe photochromic lens to make the lens appear to be a dark shade ofcolor at all times like typical sunglasses.

SPECIFIC EXAMPLES

The following examples are included to demonstrate embodiments of theinvention. Those of skill in the art, in light of the presentdisclosure, should appreciate that many changes may be made in thespecific examples that are disclosed and still obtain a like or similarresult without departing from the spirit and scope of the invention.

Example 1 Formation of a Plastic Lens by Curing With Activating Light

Formulation: 17% Bisphenol A bis(allyl carbonate) 10% 1,6 Hexanedioldimethacrylate 20% Trimethylolpropane triacrylate 21%Tetraethyleneglycol diacrylate 32% Tripropyleneglycol diacrylate 0.012%1 Hydroxycyclohexyl phenyl ketone 0.048  Methyl benzoylformate <10 ppmHydroquinone & Methylethylhydroquinone

Hydroquinone and Methylethylhydroquinone were stabilizers present insome of the diacrylate and/or triacrylate compounds obtained fromSartomer. Preferably the amount of stabilizers is minimized since thestabilizers affect the rate and amount of curing. If larger amounts ofstabilizers are added, then generally larger amounts of photoinitiatorsmust also be added.

Light Condition: mW/cm² measured at plane of sample with Spectroline DM365N Meter from Spectronics Corp. (Westbury, N.Y.)

Center Edge Top: 0.233 0.299 Bottom: 0.217 0.248

Air Flow: 9.6 standard cubic feet per minute (“CFM”) per manifold—19.2CFM total on sample

Air Temperature: 4.4 degrees Centigrade

Molds: 80 mm diameter Coming #8092 glass

Radius Thickness Concave: 170.59 2.7 Convex: 62.17 5.4

Gasket: General Electric SE6035 silicone rubber with a 3 mm. thicklateral lip dimension and a vertical lip dimension sufficient to providean initial cavity center thickness of 2.2 mm.

Filling: The molds were cleaned and assembled into the gasket. Themold/gasket assembly was then temporarily positioned on a fixture whichheld the two molds pressed against the gasket lip with about 1 kg. ofpressure. The upper edge of the gasket was peeled back to allow about27.4 grams of the monomer blend to be charged into the cavity. The upperedge of the gasket was then eased back into place and the excessmonomerwas vacuumed out with a small aspirating device. It is preferable toavoid having monomer drip onto the noncasting surface of the moldbecause a drop tends to cause the activating light to become locallyfocused and may cause an optical distortion in the final product.

Curing: The sample was irradiated for fifteen minutes under the aboveconditions and removed from the lens curing unit. The molds wereseparated from the cured lens by applying a sharp impact to the junctionof the lens and the convex mold. The sample was then postcured at 110°C. in the post-cure unit for an additional ten minutes, removed andallowed to cool to room temperature.

Results: The resulting lens measured 72 mm in diameter, with a centralthickness of 2.0 mm, and an edge thickness of 9.2 mm. The focusing powermeasured ˜5.05 diopter. The lens was water clear (“water-white”), showednegligible haze, exhibited total visible light transmission of about94%, and gave good overall optics. The Shore D hardness was about 80.The sample withstood the impact of a 1 inch steel ball dropped fromfifty inches in accordance with ANSI 280.1-1987, 4.6.4 test procedures.

Example 2 Oxygen Barrier Example #1

A liquid lens forming composition was initially cured as in a processand apparatus similar to that specified in Example 1. The compositionwas substantially the same as specified in Example 1, with the exceptionthat hydroquinone was absent, the concentration ofmethylethylhydroquinone was about 25-45 ppm, the concentration of1-hydroxycyclohexyl phenyl ketone was 0.017 percent, and theconcentration of methylbenzoylformate was 0.068 percent. The compositionunderwent the initial 15 minute cure under the “1st activating light.”The apparatus was substantially the same as described for the aboveExample 1, with the following exceptions:

1. The air flowrate on each side of the lens mold assembly was estimatedto be about 18-20 cubic feet per minute.

2. The air flowrate in and out of the chamber surrounding the lights wasvaried in accordance with the surface temperature of the lights. The airflowrate was varied in an effort to keep the temperature on the surfaceof one of the lights between 104.5° F. and 105° F.

3. The activating light output was controlled to a set point by varyingthe power sent to the lights as the output of the lights varied.

4. Frosted glass was placed between the lights and the filters used tovary the intensity of the activating light across the face of the molds.Preferably the glass was frosted on both sides. The frosted glass actsas a diffuser between the lights and these filters. This frosted glasstended to yield better results if it was placed at least about 2 mm fromthe filter, more preferably about 10-15 mm, more preferably still about12 mm, from the filter. Frosted glass was found to dampen the effect ofthe filters. For instance, the presence of the frosted glass reduced thesystems' ability to produce different lens powers by varying the light(see Example 1 and FIG. 1).

After initial cure, the lens mold assembly was removed from the curingchamber. The lens mold assembly included a lens surrounded by a frontmold, a back mold, and a gasket between the front and back molds (see,e.g., the assembly in FIG. 11).

At this point the protocol in Example 1 stated that the lens wasdemolded (see above). While demolding at this point is possible, asstated above, generally some liquid lens forming composition remained,especially in areas of the lens proximate the gasket. Therefore, thelens was not demolded as stated in Example 1. Instead, the gasket wasremoved, liquid lens forming composition was wiped off the edges of thelens, and a layer of oxygen barrier (Parafilm M) with photoinitiator waswrapped around the edges of the lens while the lens was still betweenthe molds. The Parafilm M was wrapped tightly around the edges of thelens and then stretched so that it would adhere to the lens and molds(i.e., in a manner similar to that of Saran wrap). The lens moldassembly was then placed in the post-cure unit so that the back face ofthe lens (while between the molds) could then be exposed to additionalactivating light.

This second activating light was at a substantially higher intensitythan the initial cure light, which was directed at an intensity of lessthan 10 mW/cm². The mold assembly was irradiated with ultraviolet lightfor about 22 seconds. The total light energy applied during these 22seconds was about 4500 millijoules per square centimeter (“mJ/cm²”).

It has been found that applying activating light at this point helped tocure some or all of the remaining liquid lens forming composition. Thesecond activating light step may be repeated. In this example, thesecond activating light step was repeated once. It is also possible toexpose the front or both sides of the lens to the second activatinglight.

After the second activating light was applied, the mold assembly wasallowed to cool. The reactions caused by exposure to activating lightmay be exothermic. The activating lights also tend to emit infra-redlight which in turn heats the mold assembly. The lens was then demolded.The demolded lens was substantially drier and harder than lenses thatwere directly removed from mold assemblies after the initial cure step.

Example 3 Oxygen Barrier Example #2

The protocol of Oxygen Barrier Example #1 was repeated except that priorto removal of the gasket the lens mold assembly was positioned so thatthe back face of the lens was exposed to third activating light. In thiscase the third activating light was at the same intensity and for thesame time period as one pass of the second activating light. It has beenfound that applying third activating light at this point helped to curesome or all of the remaining liquid lens forming composition so thatwhen the gasket was removed less liquid lens forming composition waspresent. All of the remaining steps in Oxygen Barrier Example #1 wereapplied, and the resultant lens was substantially dry when removed fromthe molds.

Example 4 Conductive Heating Example

A liquid lens forming composition was initially cured in a process andapparatus similar to that specified in Example 1 except for post-curetreatment, which was conducted as follows:

After the sample was irradiated for 15 minutes, the lens was placed inthe post-cure unit to receive a dose of about 1500 mJ/cm² (+/−100 mJ) ofactivating light per pass. The gasket was then removed from the moldassembly and the edges of the mold were wiped with an absorbent tissueto remove incompletely cured lens forming material proximate the moldedges. A strip of plastic material impregnated with photoinitiator waswrapped around the edges of the molds that were exposed when the gasketwas removed. Next, the mold assembly was passed through the post-cureunit once to expose the front surface of the mold to a dose of about1500 mJ/cm². The mold assembly was then passed through the post-cureunit four more times, with the back surface of the mold receiving a doseof about 1500 mJ/cm² per pass. The heat source of the post-cure unit wasoperated such that the surface of the hot plate reached a temperature of340° F. (+/−50° F.). A conformable “beanbag” container having a coveringmade of NOMEX fabric was placed on the hot plate. The containercontained glass beads and was turned over such that the portion of thecontainer that had directly contacted the hot plate (i.e., the hottestportion of the container) faced upward and away from the hot plate. Themold assembly was then placed onto the heated, exposed portion of thecontainer that had been in direct contact with the hot plate. Theconcave, non-casting face of the mold was placed onto the exposedsurface of the container, which substantially conformed to the shape ofthe face. Heat was conducted through the container and the mold memberto the lens for 13 minutes. A lens having a Shore D hardness of 84 wasformed.

Example 5 Curing Cycles

Some established cycles are detailed in the table below for threesemi-finished mold gasket sets: a 6.00D base curve, a 4.50D base curve,and a 3.00D base curve. These cycles have been performed with coolingair, at a temperature of about 56° F., directed at the front and backsurfaces of a mold assembly. Frosted diffusing window glass waspositioned between the samples and the lamps, with a layer of PO-4acrylic material approximately 1 inch below the glass. A top lightintensity was adjusted to 760 microwatts/cm² and a bottom lightintensity was adjusted to 950 microwatts/cm², as measured at about theplane of the sample. A Spectroline meter DM365N and standard detectorstage were used. An in-mold coating as described in U.S. Pat. No.5,529,728 to Buazza et. al. was used to coat both the front and backmolds.

BASE CURVE Mold Sets 6.00 4.50 3.00 Front Mold 5.95 4.45 2.93 Back Mold6.05 6.80 7.80 Gasket −5.00  13 mm   16 mm Resulting Semifinished BlankDiameter  74 mm  76 mm   76 mm Center Thickness 9.0 mm  7.8 mm  7.3 mmEdge Thickness 9.0 mm 11.0 mm 15.0 mm Mass  46 grams  48 grams   57Curing Cycle Variables grams Total Cycle Time 25:00 25:00 35:00 InitialExposure 4:40 4:40 4:35 Number of Pulses 4 4 4 Timing (in seconds) andDuration of Pulses @ Elapsed Time From Onset of Initial Exposure Pulse 115@10:00 15@10:00 15@13:00 Pulse 2 15@15:00 15@15:00 15@21:00 Pulse 330@19:00 30@19:00 20@27:00 Pulse 4 30@22:00 30@22:00 30@32:00

FIGS. 26, 27, and 28 each show temperature profiles of theabove-detailed cycles for a case where the activating light exposure iscontinuous and a case where the activating light delivery is pulsed. InFIGS. 26-28, “Io” denotes the initial intensity of the activating lightused in a curing cycle. The phrase “Io=760/950” means that the lightintensity was adjusted to initial settings of 760 microwatts/cm² for thetop lamps and 950 microwatts/cm² for the bottom lamps. The “interiortemperature” of FIGS. 26-28 refers to a temperature of the lens formingmaterial as measured by a thermocouple located within the mold cavity.

Example 6 Pulse Method Using a Medium Pressure Vapor Lamp

An eyeglass lens was successfully cured with activating light utilizinga medium pressure mercury vapor lamp as a source of activating light(i.e., the UVEXS Model 912 previously described herein). The curingchamber included a six inch medium pressure vapor lamp operating at apower level of approximately 250 watts per inch and a defocused dichroicreflector that is highly activating light reflective. A high percentageof infrared radiation was passed through the body of the reflector sothat it would not be directed toward the material to be cured. Thecuring chamber further included a conveyer mechanism for transportingthe sample underneath the lamp. With this curing chamber, the transportmechanism was set up so that a carriage would move the sample from thefront of the chamber to the rear such that the sample would movecompletely through an irradiation zone under the lamp. The sample wouldthen be transported through the zone again to the front of the chamber.In this manner the sample was provided with two distinct exposures percycle. One pass, as defined hereinafter, consists of two of thesedistinct exposures. One pass provided a dosage of approximately 275millijoules measured at the plane of the sample using an InternationalLight IL 1400 radiometer equipped with a XRL 340 B detector.

A lens cavity was created using the same molds, lens formingcomposition, and gasket as described in Example 7 below. The reactioncell containing the lens forming material was placed on a supportingstage such that the plane of the edges of the convex mold were at adistance of approximately 75 mm from the plane of the lamp. The lenscavity was then exposed to a series of activating light doses consistingof two passes directed to the back surface of the mold followedimmediately by one pass directed to the front surface of the mold.Subsequent to these first exposures, the reaction cell was allowed tocool for 5 minutes in the absence of any activating radiation at an airtemperature of 74.6 degrees F and at an air flow rate of approximately15 to 25 scf per minute to the back surface and 15 to 25 scf to thefront surface of the cell. The lens cavity was then dosed with one passto the front mold surface and returned to the cooling chamber for 6minutes. Then the back surface was exposed in one pass and then wascooled for 2 minutes. Next, the front surface was exposed in two passesand then cooled for 3.5 minutes. The front surface and the back surfacewere then each exposed to two passes, and the gasket was removed toexpose the edges of the lens. A strip of polyethylene film impregnatedwith photoinitiator was then wrapped around the edge of the lens and thefront and back surfaces were exposed to another 3 passes each. The backsurface of the cell was then placed on the conductive thermal in-moldpostcure device using a “bean-bag” container filled with glass beads ona hot plate at about 340° F. described previously (see Example 4) for atime period of 13 minutes, after which the glass molds were removed fromthe finished lens. The finished lens exhibited a distance focusing powerof −6.09 diopters, had excellent optics, was aberration-free, was 74 mm.in diameter, and had a center thickness of 1.6 mm. During the coolingsteps , a small surface probe thermistor was positioned against theoutside of the gasket wall to monitor the reaction. the results aresummarized below.

Approx. Elapsed Time After Activating Light Gasket Wall TemperatureActivating Light Dose Dose (min) (° F.) 2 passes to back surface 0 Notrecorded and 1 pass to front surface 1 80.5 2 79.7 3 79.0 4 77.1 5 76.21 pass to front surface 0 Not recorded 1 83.4 2 86.5 3 84.6 4 Notrecorded 5 81.4 6 79.5 1 pass to back surface 0 Not recorded 1 79.3 279.0 2 passes to front surface 0 Not recorded 1 78.4 2 77.8 3 77.0 3.576.7

Example 7 Pulse Method Using a Single Xenon Flash Lamp

An eyeglass lens was successfully cured with activating light utilizinga xenon flash lamp as a source of activating light. The flash lamp usedwas an Ultra 1800 White Lightning photographic strobe, commerciallyavailable from Paul C. Buff Incorporated of Nashville, Tenn. This lampwas modified by replacing the standard borosilicate flash tubes withquartz flash tubes. A quartz flash tube is preferred because some of theactivating light generated by the arc inside the tube tends to beabsorbed by borosilicate glass. The strobe possessed two semicircularflash tubes that trigger simultaneously and the flash tubes werepositioned to form a ring approximately 73 millimeters in diameter. Thehole in the reflector behind the lamps, which normally contains amodeling lamp for photographic purposes, was covered with a flat pieceof highly-polished activating light reflective material that iscommercially available under the trade name of Alzac from Ultra VioletProcess Supply of Chicago, Ill. The power selector switch was set tofull power. The activating light energy generated from one flash wasmeasured using an International Light IL 1700 Research Radiometeravailable from International Light, Incorporated of Newburyport, Mass.The detector head was an International Light XRL 340 B, which issensitive to radiation in the 326 nm to 401 nm region. The window of thedetector head was positioned approximately 35 mm from the plane of theflash tubes and was approximately centered within the ring formed by thetubes.

A mold cavity was created by placing two round 80 mm diameter crownglass molds into a silicone rubber ring or gasket that possessed araised lip around its inner circumference. The edges of the glass moldsrested upon the raised lip to form a sealed cavity in the shape of thelens to be created. The inner circumference of the raised lipcorresponded to the edge of the finished lens. The concave surface ofthe first mold corresponded to the front surface of the finished lensand the convex surface of the second mold corresponded to the backsurface of the finished lens. The height of the raised lip of the rubberring into which the two glass molds are inserted controls the spacingbetween the two glass molds, thereby controlling the thickness of thefinished lens. By selecting proper gaskets and first and second moldsthat possess various radii of curvature, lens cavities may be created toproduce lenses of various powers.

A lens cavity was created by placing a concave glass mold with a radiusof curvature of 407.20 mm and a convex glass mold with a radius ofcurvature of 65.26 mm into a gasket which provided spacing between themolds of 1.8 mm measured at the center of the cavity. Approximately 32grams of a lens forming monomer was charged into the cavity. The lensforming material used for this test was OMB-91 lens monomer. Thereaction cell containing the lens forming material was placedhorizontally on a supporting stage such that the plane of the edges ofthe convex mold were at a distance of approximately 30 mm from the planeof the flash tubes and the cell was approximately centered under thelight source.

The back surface of the lens cavity was then exposed to a first seriesof 5 flashes, with an interval of approximately 4 seconds in betweeneach flash. The cell was then turned over and the front surface wasexposed to another 4 flashes with intervals of about 4 seconds inbetween each flash. It is preferable to apply the first set of flashesto the back surface to start to cure the material so that any airbubbles in the liquid monomer will not migrate from the edge of thecavity to the center of the optical zone of the lens. Subsequent tothese first nine flashes, the reaction cell was allowed to cool for fiveminutes in the absence of any activating radiation. To cool the reactioncell, air at a temperature of 71.4 degrees F and at a flow rate ofapproximately 15 to 25 scf per minute was applied to the back surfaceand air at a temperature of 71.4 degrees F and at a flow rate ofapproximately 15 to 25 scf per minute was applied to the front surfaceof the cell. The back surface of the lens cavity was then dosed with onemore flash and returned to the cooling chamber for four minutes.

Next, the cell was exposed to one flash on the front surface and cooledin the cooling chamber for seven minutes. Then the cell was exposed toone flash on the front surface and one flash on the back surface andcooled for three minutes. Next, the cell was exposed to two flashes onthe front surface and two flashes on the back surface and cooled forfour and a half minutes. The cell was then exposed to five flashes eachto the back surface and front surface, and the gasket was removed toexpose the edges of the lens. A strip of polyethylene film impregnatedwith photoinitiator (Irgacure 184) was then wrapped around the edge ofthe lens, and the cell was exposed to another five flashes to the frontsurface and fifteen flashes to the back surface. The back surface of thecell was then placed on the conductive thermal in-mold postcure device(i.e., “bean bags” filled with glass beads sitting on a hot plate atapprox. 340° F.) as described previously (see conductive heating exampleabove) for a time period of 13 minutes, after which the glass molds wereremoved from the finished lens. The finished lens exhibited a distancefocusing power of −6.16 diopters and a +2.55 bifocal add power, hadexcellent optics, was aberration-free, was 74 mm. in diameter, and had acenter of thickness of 1.7 mm. During the cooling steps, a small surfaceprobe thermistor was positioned against the outside of the gasket wallto monitor the reaction. The results are summarized below.

Elapsed Time Gasket Wall Dose From Dose (min) Temperature (F) 5 flashesto back surface 0 Not recorded and 4 flashes to front surface 1 Notrecorded 2 78.4 3 77.9 4 76.9 5 75.9 1 flash to back surface 0 Notrecorded 1 76.8 2 77.8 3 78 4 77.8 1 flash to front surface 0 Notrecorded 1 79.4 2 81.2 3 81.1 4 79.7 5 78.7 6 77.5 7 77.4 1 flash tofront surface and 0 Not recorded 1 flash to back surface 1 78.8 2 78.8 378.0 2 flashes to front surface and 2 0 Not recorded flashes to backsurface 1 80.2 2 79.8 3 78.3 4 76.7 4.5 76.3

Example 8 Improved Curing Example

an 80 mm diameter glass progressive addition mold with a nominaldistance radius of curvature of −6.00 diopters and a +2.50 diopterbifocal add power was sprayed with a mixture of isopropyl alcohol anddistilled water in equal parts and wiped dry with a lint free papertowel. The progressive mold was lenticularized to provide an opticalzone 68 mm in diameter along the 180 degree meridian and 65 mm indiameter along the 90 degree meridian. The non-casting face of the moldwas mounted to a suction cup, which was attached to a spindle. Thespindle was placed on a spin coat unit. A one inch diameter pool ofliquid Primer was dispensed into the center of the horizontallypositioned glass mold from a soft polyethylene squeeze bottle equippedwith a nozzle with an orifice diameter of approximately 0.040 inches.The composition of the Primer is discussed in detail below (see ScratchResistant Lens Formation Process Example).

The spin motor was engaged to rotate the mold at a speed ofapproximately 850 to 900 revolutions per minute, which caused the liquidmaterial to spread out over the face of the mold. Immediatelythereafter, a steady stream of an additional 1.5 to 2.0 grams of Primermaterial was dispensed onto the casting face of the spinning mold withthe nozzle tip positioned at a 45 degree angle approximately 12 mm fromthe mold face such that the stream was flowing with the direction ofrotation of the mold. The stream of Primer material was directed firstat the center of the mold face and then dispensed along the radius ofthe mold face in a direction from the center toward the edge of the moldface. The solvent present in the Primer was allowed to evaporate off for8 to 10 seconds while the mold was rotated. The rotation was stopped andthe Primer coat present on the mold was cured via two exposures to theactivating light output from the medium pressure mercury vapor lamp,totaling approximately 300 mJ/cm².

The spin motor was again engaged and approximately 1.5 to 2.0 grams ofHC8-H Hard Coat (see description below), commercially available from theFastCast Corporation of Louisville, Ky. was dispensed onto the spinningmold in a similar fashion as the Primer coat. The solvent present in theHC8-H was allowed to evaporate off for 25 seconds while the mold wasrotated. The rotation was stopped and the HC8-H coat was cured in thesame manner as the Primer coat.

The mold was removed from the FlashCure unit and assembled into asilicone rubber gasket in combination with a cleaned convex moldpossessing a radius of curvature of +2.00 diopters. The raised lippresent on the inner circumference of the rubber gasket provided aspacing of 6.3 mm between the two molds at the center point. Themold/gasket assembly was positioned on a filling stage and the edge ofthe gasket was peeled back to permit the cavity to be filled with OMB-91lens forming composition, commercially available from the FastCastCorporation of Louisville, Ky. The edge of the gasket was returned toits sealing relationship with the edges of the molds and the excess lensforming composition was vacuumed off the non-casting surface of the backmold with a suction device. The filled mold/gasket assembly was placedon a stage in a lens curing unit and subjected to four exposures of theactivating light output from the six inch medium pressure mercury vaporlamp, totaling approximately 600 mJ/cm².

Immediately following this initial dose of high intensity activatinglight, the assembly was continuously exposed to streams of air having atemperature of 42° F. while being irradiated with very low intensityactivating light for eight minutes. The light intensity measuredapproximately 90 microwatts/cm² from above plus approximately 95microwatts/cm² from below, according to the plus lens light distributionpattern called for by the manufacturer. The lamp racks are typicallyconfigured to deliver activating light having an intensity of about 300microwatt/cm² for the standard fifteen minute curing cycle. Thereduction in activating light intensity was accomplished by inserting atranslucent high density polyethylene plate into the light distributionfilter plate slot along with the plus lens light distribution plate. Atranslucent high density polyethylene plate was positioned between thefront mold member and one light distribution plate and between the backmold member and the other light distribution plate.

The non-casting surface of the back mold was subsequently exposed tofour doses of high intensity activating light totaling approximately1150 mJ/cm². The gasket was stripped from the assembly and residualuncured material wiped from the exposed edge of the lens. An oxygenbarrier strip (polyethylene) was wrapped around the edge of the lens andthe mold was exposed to two more doses of high intensity activatinglight totaling 575 mJ/cm² to the non-casting surface of the front moldfollowed by eight more flashes to the non-casting surface of the backmold totaling 2300 mJ/cm².

The non-casting surface of the back mold was placed in contact with athermal transfer pad, commercially available from the FastCastCorporation of Louisville, Ky., at a temperature of approximately 150 to200° F. for thirteen minutes. The assembly was removed from the thermaltransfer pad and the back mold was removed with a slight impact from anappropriately sized wedge. The front mold with the lens attached theretowas placed in a container of room temperature water and the lensseparated from the front mold. The now-finished lens was sprayed with amixture of isopropyl alcohol and water in equal parts and wiped dry. Thelens read +3.98 D with an addition power of +2.50, was clear,non-yellow, and exhibited good optics.

Example 9 Scratch Resistant Lens Formation Example

A first coating composition, hereinafter referred to as “Primer”, wasprepared by mixing the following components by weight:

93.87% acetone;

3.43% SR-399 (dipentaerythritol pentaacrylate), available from Sartomer;

2.14% CN-104 (epoxy acrylate), available from Sartomer;

0.28% Irgacure 184 (1-hydroxycyclohexylphenylketone), available fromCiba-Geigy; and

0.28% Darocur 1173 (2-hydroxy-2-methyl-1-phenyl-propan-1-one) availablefrom Ciba-Geigy.

A second coating composition, hereinafter referred to as “HC8-H” wasprepared by mixing the following components by weight:

84.69% 1-methoxy 2-propanol;

9.45% SR-399 (dipentaerythritol pentaacrylate), available from Sartomer;

4.32% SR601 (ethoxylated bisphenol A diacrylate), available fromSartomer; and

1.54% Irgacure 184 (1-hydroxycyclohexyl phenyl ketone), available fromCiba-Geigy.

Each of these coating compositions was prepared by first dissolving themonomers into the solvent, then adding the photoinitiators, mixing well,and finally passing the composition through a one micron filter prior touse.

An 80 mm diameter glass, 28 mm flattop mold with a distance radius ofcurvature of −6.00 diopters and a +2.00 diopter bifocal add power weresprayed with a mixture of isopropyl alcohol and distilled water in equalparts. The flattop mold was wiped dry with a lint free paper towel. Thenon-casting face of the mold was mounted to a suction cup, which wasattached to a spindle. The spindle was placed on the spin coating unit.

A one inch diameter pool of liquid Primer was dispensed into the centerof the horizontally positioned glass mold. The Primer was dispensed froma soft polyethylene squeeze bottle equipped with a nozzle having anorifice diameter of approximately 0.040 inches. A spin motor of thespinning device was engaged to rotate the mold at a speed ofapproximately 850 to 900 revolutions per minute, causing the liquidPrimer to spread out over the face of the mold. Immediately thereafter,a steady stream of an additional 1.5 to 2.0 grams of Primer material wasdispensed onto the casting face of the spinning mold. The stream ofPrimer material was directed onto the casting face with the nozzle tippositioned at a 45 degree angle approximately 12 mm from the mold face.This positioning of the nozzle tip made the-stream to flow with thedirection of rotation of the mold. The stream of Primer material wasdirected first at the center of the mold face and then dispensed alongthe radius of the mold face in a direction from the center toward theedge of the mold face.

The solvent present in the Primer was allowed to evaporate off for 8 to10 seconds during rotation of the mold. The rotation was stopped and thePrimer coat which remained on the mold was cured via two exposures tothe activating output from a medium pressure mercury vapor lamp,totaling approximately 300 mJ/cm². All light intensity/dosagemeasurements cited herein were taken with an International Light IL-1400Radiometer equipped with an XLR-340B Detector Head, both commerciallyavailable from International Light, Inc. of Newburyport, Mass.

Upon exposure to the activating light, the spin motor was again engagedand approximately 1.5 to 2.0 grams of HC8-H Hard Coat, commerciallyavailable from the FastCast Corporation of Louisville, Ky. was dispensedonto the spinning mold in a similar fashion as the Primer coat. Thesolvent present in the HC8-H was allowed to evaporate off for 25 secondswhile the mold was spinning. The rotation was stopped, and the HC8-Hcoat was cured in the same manner as the Primer coat.

The mold was removed from the spin coating unit and assembled into asilicone rubber gasket in combination with a cleaned convex moldpossessing a radius of curvature of +7.50 diopters. The raised lippresent on the inner circumference of the rubber gasket provided aspacing of 1.8 mm between the two molds at the center point. At thispoint, the mold/gasket assembly was positioned on a filling stage andthe edge of the gasket was peeled back to permit the cavity to be filledwith OMB-91 lens forming composition, commercially available from theFastCast Corporation of Louisville, Ky. The edge of the gasket wasreturned to its sealing relationship with the edges of the molds and theexcess lens forming composition was vacuumed off the non-casting surfaceof the back mold with a suction device.

The filled mold/gasket assembly was transferred from the filling stageto a lens curing unit. While in the lens curing unit, the assembly wascontinuously irradiated with activating light from both sides for aperiod of 15 minutes at approximately 300 microwatts/cm² from above andat approximately 350 microwatts/cm² from below, according to the minuslens light distribution pattern called for by the manufacturer. Duringthe irradiation, the casting cell was continuously exposed to streams ofair having a temperature of 42° F.

The non-casting surface of the back mold was exposed to four doses ofhigh intensity activating light totaling approximately 1150 mJ/cm². Thegasket was stripped from the assembly and residual uncured material waswiped from the exposed edge of the lens. An oxygen barrier strip(polyethylene) was wrapped around the edge of the lens. The mold/gasketassembly was exposed to two more doses of high intensity activatinglight, wherein 575 mj/cm² total was directed to the non-casting surfaceof the front mold. Subsequently, eight more flashes of the activatinglight were directed to the non-casting surface of the back mold,totaling 2300 mj/cm².

The non-casting surface of the back mold was placed in contact with athermal transfer pad, commercially available from the FastCastCorporation of Louisville, Ky., at a temperature of approximately 150 to200° F. for thirteen minutes. The mold/gasket assembly was removed fromthe thermal transfer pad, and the back mold was removed with a slightimpact from an appropriately sized wedge. The front mold with the lensattached thereto was placed in a container of room temperature water.While within the water, the lens became separated from the front mold.The now-finished lens was sprayed with a mixture of isopropyl alcoholand water in equal parts and wiped dry.

The lens was positioned in a holder and placed into a heated dye pot for5 minutes. The dye pot contained a solution of BPI Black, commerciallyavailable from Brain Power, Inc. of Miami, Fla., and distilled water ata temperature of approximately 190 degrees F. The lens was removed fromthe dye pot, rinsed with tap water, and wiped dry. The lens exhibited atotal visible light absorbance of approximately 80%. When inspected forcosmetic defects on a light table, no pinhole defects were observed.Further, the tint which had been absorbed by the back surface of thelens was found to be smooth and even.

Example 10 Formation of a Plastic Lens Containing Photochromic Material

A polymerizable mixture of PRO-629 (see above for a description of thecomponents of PRO-629), photochromic pigments, and aphotoinitiator/co-initiator system was prepared according to thefollowing procedure. A photochromic stock solution was prepared bydissolving the following pigments into 484 grams of HDDMA.

Pigment grams % by wt. Dye #94 1.25 0.250% Dye #266 0.45 0.090%Variacrol Red PNO 2.66 0.532% Variacrol Yellow L 1.64 0.328% ReversacolCorn Yellow 3.58 0.716% Reversacol Berry Red 2.96 0.590% Reversacol SeaGreen 2.17 0.434% Reversacol Palatinate Purple 1.29 0.258% Total 16.03.200%

Dye #94 and Dye #266 are indilino-spiropyrans commercially availablefrom Chroma Chemicals, Inc. in Dayton, Ohio. Variacrol Red PNO is aspiro-napthoxazine material and Variacrol Yellow L is a napthopyranmaterial, both commercially available from Great Lakes Chemical in WestLafayette, Ind. Reversacol Corn Yellow and Reversacol Berry Red arenapthopyrans and Reversacol Sea Green, and Reversacol Palatinate Purpleare spiro-napthoxazine materials commercially available from KeystoneAnaline Corporation in Chicago, Ill.

The powdered pigments were weighed and placed in a beaker. The HDDMA wasadded to the powdered pigments, and the entire mixture was heated to atemperature in the range from about 50° C. to 60° C. and stirred for twohours. Subsequently, the photochromic stock solution was cooled to roomtemperature and then gravity fed through a four inch deep bed ofaluminum oxide basic in a one inch diameter column. Prior to passing thestock solution through the alumina, the alumina was washed with acetoneand dried with air. The remaining HDDMA was forced out of the aluminawith pressurized air. It is believed that this filtration step removesany degradation by-products of the photochromic pigments and/or anyimpurities present in the mixture. After the filtration step, the stocksolution was passed through a 1 micron filter to remove any aluminaparticles which may have passed out of the column with the stocksolution.

A photoinitiator stock solution containing a photoinitiator combinedwith an ultraviolet/visible light absorber was also prepared by mixing2.56 grams of CGI-819 and 0.2 grams of Tinuvin 400, anultraviolet/visible light absorber commercially available from CibaAdditives of Tarrytown, N.Y., with 97.24 grams of PRO-629. The stocksolution was stirred for two hours at room temperature in the absence oflight. The photoinitiator stock solution was then filtered by passing itthrough a layer of alumina and a one micron filter. The stock solutionwas placed in an opaque polyethylene container for storage.

A background dye stock solution was prepared by mixing 50 grams of a 422ppm solution of A241/HDDMA, 50 grams of a 592 ppm solution ofThermoplast Red 454/HDDMA, 50 grams of 490 ppm solution of Zapon Brown286/HDDMA, 50 grams of 450 ppm solution of Zapon Brown 287/HDDMA, 50grams of 1110 ppm solution of Oil Soluble Blue II/HDDMA, and 50 grams ofa 1110 ppm solution of Thermoplast Blue P/HDDMA, all with 700 grams ofPRO-629. The entire mixture was heated to a temperature ranging fromabout 50° C. to 60° C. and subsequently stirred for two hours.

A lens forming composition was prepared by adding 12.48 grams of theabove described photochromic stock solution, 10 grams of thephotoinitiator stock solution, 27 grams of the background dye stocksolution, and 7.3 grams of the NMDEA co-initiator to 943.22 grams ofPRO-629. The components of the lens forming composition were stirred atroom temperature for several minutes until well mixed. This compositionis hereafter referred to as PC #1. The PC#1 contained the followingamounts of components.

Component Amount Tripropyleneglycol diacrylate 31.16%Tetraethyleneglycol diacrylate 20.45% Trimethylolpropane triacrylate19.47% Bisphenol A bis allyl carbonate 16.55% Hexanediol dimethacrylate11.56% Dye #94 31.20 ppm Dye #266 11.20 ppm Variacrol Red PNO 66.40 ppmVariacrol Yellow L 40.90 ppm Reversacol Corn Yellow 89.30 ppm ReversacolBerry Red 73.60 ppm Reversacol Sea Green 54.20 ppm Reversacol PalatinatePurple 32.20 ppm A241 0.57 ppm Thermoplast Red 454 0.80 ppm Zapon Brown286 0.66 ppm Zapon Brown 287 0.61 ppm Oil Soluble Blue II 1.50 ppmThermoplast Blue 1.50 ppm CGI-819 255.90 ppm NMDEA 0.73% Tinuvin 40020.00 ppm

An 80 mm diameter concave glass progressive addition mold having adistance radius of curvature of 6.00 diopters and a +1.75 diopterbifocal add power was sprayed with a mixture of isopropyl alcohol anddistilled water in equal parts and wiped dry with a lint free papertowel. The mold was then mounted with its casting face upward on thecenter of a stage. The mold was fixed securely to the stage using threeequidistant clip-style contact points to hold the periphery of the mold.The mold stage had a spindle attached to it which was adapted to connectto a spin coating device. The mold stage, with the mold affixed, wasplaced within the spin coating device. The mold was rotated atapproximately 750 to 900 revolutions per minute. A stream of isopropylalcohol was directed at the casting surface while the casting surfacewas simultaneously brushed with a soft camel hair brush to clean thesurface. After the cleaning step, the mold surface was dried bydirecting a stream of reagent grade acetone over the surface andallowing it to evaporate off, all while continuing the rotation of themold.

The rotation of the mold was then terminated and a one inch diameterpool of a liquid coating composition was dispensed into the center ofthe horizontally positioned glass mold from a soft polyethylene squeezebottle equipped with a nozzle having an orifice diameter ofapproximately 0.040 inches. The spin motor was engaged to rotate themold at a speed of approximately 750 to 900 revolutions per minute,causing the liquid material to spread out over the face of the mold.Immediately thereafter, a steady stream of an additional 1.5 to 2.0grams of the coating composition was dispensed onto the casting face ofthe spinning mold. The stream was moved from the center to the edge ofthe casting face with a nozzle tip positioned at a 45° angleapproximately 12 mm from the mold face. Thus, the stream was flowingwith the direction of rotation of the mold.

The solvent present in the coating composition was allowed to evaporatewhile rotating the mold for 10 to 15 seconds. The rotation was stopped,and then the coating composition on the mold was cured via a totalexposure of approximately 300 mJ/cm² of activating light. The light wasprovided from a medium pressure mercury vapor lamp. All lightintensity/dosage measurements cited herein were taken with anInternational Light IL-1400 Radiometer equipped with an XLR-340BDetector Head, both commercially available from International Light,Inc. of Newburyport, Mass. At this point, the spin motor was againengaged and approximately 1.5 to 2.0 grams of additional coatingcomposition was dispensed onto the spinning mold. The solvent of thecomposition was allowed to evaporate, and the composition was cured in asimilar fashion to the first layer of coating composition.

The above described coating composition comprised the followingmaterials:

Material % by wt. Irgacure 184 0.91% Tinuvin 770 0.80% CN-104 2.00%SR-601 1.00% SR-399 8.60% Acetone 26.00% Ethanol 7.00% 1-Methoxypropanol53.69%

Irgacure 184 is a photoinitiator commercially available from CibaAdditives, Inc. CN-104 is an epoxy acrylate oligomer, SR-601 is anethoxylated bisphenol A diacrylate, and SR-399 is dipentaerythritolpentaacrylate, all available from Sartomer Company in Exton, Pa. Theacetone, the ethanol, and the 1-methoxypropanol were all reagent gradesolvents. The Tinuvin 770 improves the impact resistance of the lens andis available from Ciba Additives, Inc.

An 80 mm diameter convex mold with radii of curvature of 6.80/7.80diopters was cleaned and coated using the same procedure described aboveexcept that no pooling of the coating composition occurred in the centerof the mold when the composition was dispensed thereto.

The concave and convex molds were then assembled together with asilicone rubber gasket. A raised lip on the inner circumference of therubber gasket provided a spacing of 2.8 mm between the two molds at thecenter point. At this point the mold/gasket assembly was positioned on afilling stage. The edge of the gasket was peeled back to permit thecavity to be filled with PC #1 lens forming composition. The edge of thegasket was returned to its sealing relationship with the edges of themolds, and the excess lens forming composition was vacuumed from thenon-casting surface of the back mold with a suction device. The filledmold/gasket assembly was then transferred from the filling stage to alens curing unit. The assembly was placed with the back mold facingupward on a black stage configured to hold the mold/gasket assembly.

An activating light filter was then placed on top of the back mold. Thefilter was approximately 80 mm in diameter which is the same as the molddiameter. The filter also had a spherical configuration with a centerthickness of 6.7 mm and an edge thickness of 5.5 mm. The filter wastaken from a group of previously made filters. These filters were formedby using eyeglass lens casting molds and gaskets to create cavities thatwere thickest in the center (a plus spherical cavity) and cavities thatwere thinnest in the center (a minus spherical cavity). A toriccomponent was also incorporated with some of these cavities to formcompound cavities.

The filter cavities were filled with an activating light curablecomposition comprising by weight: 99.37% PRO-629, 0.35% K-Resin, 0.27%NMDEA, 121 ppm CGI-819, and 10 ppm Tinuvin 400. K-resin is astyrene-butadiene copolymer commercially available from PhillipsChemical Company. To form this composition, the K-resin was firstdissolved in toluene. An appropriate amount of the K-resin toluenesolution was added to the PRO-629, and then the toluene was evaporatedoff by heat and stirring. The NMDEA, CGI-19, and the Tinuvin 400 werethen added to the PRO-629/K-Resin solution. The compositions containedin the cavities were cured by exposure to activating light. When thecured article was removed from the mold cavity, it exhibited a highdegree of haze caused by the incompatibility of the PRO-629. and theK-Resin. In the strictest sense of the word, it should be noted thatthese filters were not “lenses” because their function was not to focuslight but rather to scatter and diffuse light.

The mold/gasket assembly and the filter were then irradiated with fourconsecutive doses of activating light totaling approximately 1150mJ/cm², as previously measured at the plane of the mold cavity with nofilter or any other intervening media between the light source and theplane. The mold/gasket assembly was then turned over on the stage sothat the front mold was facing upward. The mold/gasket assembly wasfurther rotated 90 degrees around the paraxial axis from its originalposition. The light filter was then placed over the front mold. Theentire assembly was then exposed to two more doses of activating lighttotaling approximately 575 mJ/cm². The mold/gasket assembly was removedfrom the curing chamber. The gasket was removed from the molds, and theexposed edge of the lens was wiped to remove any residual liquid. Themolds with lens were then placed in a vertical orientation in a rack,and the non-casting faces of both the front and back molds were exposedto ambient room temperature air for a period of approximately tenminutes. Then, without the aforementioned light filter in place, themold assembly was dosed with four exposures totaling 600 mJ/cm² directedtoward the back mold and two exposures totaling 300 mJ/cm² directedtoward the front mold.

Subsequent to these exposures, the junction of the back mold and thelens was scored with the edge of a brass spatula. The back mold was thenremoved from the lens by positioning an appropriate sized Delrin wedgebetween the front and back molds and applying a sharp impact to thewedge. The lens, along with the front mold to which it was attached, washeld under running tap water and simultaneously brushed with a softbrush to remove any flakes or particles of polymer from the edges andsurface of the lens. The front mold was then separated from the lens bybreaking the seal between the two with the point of a pin pressedagainst the junction of the front mold and the lens. The lens was thenplaced concave side upward on a lens stage of similar design to the moldstage, except that the peripheral clips were configured to secure asmaller diameter workpiece. The lens stage, with the lens affixed, waspositioned on the spin coating unit and rotated at about 750 to 900revolutions per minute. A stream of isopropyl alcohol was directed atthe concave surface while simultaneously brushing the surface with asoft, clean brush.

After brushing, a stream of isopropyl alcohol was directed at thesurface of the lens, and the rotation was continued for a period ofapproximately 30 seconds until the lens was dry. The lens was turnedover on the stage so that the convex surface of the lens faced upward.Then the cleaning procedure was repeated on the convex surface. With theconvex surface facing upward, the lens was dosed with four exposures ofactivating light totaling approximately 1150 mJ/cm². The lens was againturned over on the stage such that the concave surface was upward. Thelens was subjected to an additional two exposures totaling 300 mJ/cm².The lens was removed from the stage and placed in a convection oven at115° C. for five minutes. After annealing the lens, it was removed fromthe oven and allowed to cool to room temperature. At this point the lenswas ready for shaping by conventional means to fit into an eyeglassframe.

The resulting lens was approximately 72 mm in diameter. The lens had acenter thickness of 2.6 mm, a distance focusing power of −0.71-1.00diopters, and a bifocal addition strength of 1.74 diopters. The lensappeared to have a bleached color of tan. Also, the lens that was formedexhibited approximately 75% visible transmittance as measured with aHoya ULT-3000 meter. The lens was exposed to midday sunlight at atemperature of approximately 75° F. for 3 minutes. After being exposedto sunlight, the lens exhibited a gray color and a visible lighttransmittance of approximately 15%. The optics of the lens appeared tobe crisp, without aberrations in either the distance or the bifocalsegment regions. The same lens forming composition was cured to form aplano lens so that the lens could be scanned with a Hewlett PackardModel 8453 UV-Vis spectrophotometer. See FIG. 30 for a plot of %transmittance versus wavelength (nm), as exhibited by the plano lens inits lightened state (i.e., without sunlight exposure). The lensexhibited very little transmittance of light at wavelengths below about370 nm.

The eyeglass lens of this example was formed from a lens formingcomposition included ultraviolet/visible light absorbing photochromiccompounds by using activating light. Since photochromic pigments tend toabsorb ultraviolet/visible light strongly, the activating light mightnot have penetrated to the depths of the lens forming composition. Thelens forming composition, however, contained a co-initiator inconjunction with a photoinitiator to help promote the curing of theentire lens forming composition. The present example thus demonstratesthat a photochromic lens containing both a photoinitiator and aco-initiator may be cured using activating light to initiatepolymerization of the lens forming composition.

Example 11 Casting a Colorless Lens Containing Ultraviolet/Visible LightAbsorbers

According to a preferred embodiment, a polymerizable mixture of PRO-629(see above for a description of the components of PRO-629), colorlessultraviolet/visible light absorbing compounds, an ultravioletstabilizer, background dyes, and a photoinitiator/co-initiator packagewas prepared according to the following procedure. Six separate stocksolutions were prepared. One stock solution contained thephotoinitiator, two stock solutions contained ultraviolet/visible lightabsorbing compounds, one stock solution contained co-initiators, onestock solution contained an ultraviolet light stabilizer, and one stocksolution contained a background dye package. Each of these stocksolutions were treated by passing them through a one inch diametercolumn packed with approximately 30 grams of alumina basic. It isbelieved that this step reduced the impurities and trapped the acidicbyproducts present in each of the additives to the PRO-629. Thefollowing is a detailed description of the preparation of thepolymerizable mixture mentioned above.

About 500 grams of a photoinitiator stock solution was prepared bydissolving 2.5% by weight of bis(2,6-dimethoxybenzoyl)(2,4,4-trimethyl-phenyl) phosphine oxide (CGI-819 commercially availablefrom Ciba Additives) in Pro-629. This mixture was passed through analumina basic column in the dark.

About 500 grams of the ultraviolet light absorber stock solution wasprepared by dissolving 2.5% by weight of2(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethyl)phenol (98% purity) inPRO-629. This mixture was also passed through an alumina basic column.

About 500 grams of a co-initiator stock solution was prepared by mixing70% by weight of CN-384 (a reactive amine co-initiator commerciallyavailable from Sartomer Company) in Pro-629. This mixture was passedthrough an alumina basic column.

About 271 grams of an ultraviolet light stabilizer stock solution wasprepared by mixing 5.55% by weight of Tinuvin 292 in PRO-629. Thismixture was passed through an alumina basic column.

About 250 grams of an ultraviolet/visible light absorber stock solutionwas prepared by mixing 5.0% Tinuvin 400 (a mixture of2-[4-((2-hydroxy-3-dodecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazineand2-[4-((2-hydroxy-3-tridecyloxypropyl)-oxy)-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine)by weight in PRO-629. This mixture was passed through an alumina basiccolumn.

About 1000 grams of a background dye stock solution was prepared bymixing about 50 grams of a 592 ppm solution of Thermoplast Red454/HDDMA, 50 grams of 490 ppm solution of Zapon Brown 286/HDDMA, 50grams of 450 ppm solution of Zapon Brown 287/HDDMA, 50 grams of 1110 ppmsolution of Oil Soluble Blue II/HDDMA, and 50 grams of a 1110 ppmsolution of Thermoplast Blue P/HDDMA, all with 750 grams of PRO-629. Theentire mixture was heated to a temperature between about 50° and 60° C.and stirred for two hours. This mixture was passed through an aluminabasic column.

About 250 grams of CN-386 (a reactive amine co-initiator commerciallyavailable from Sartomer Company) was passed through an alumina basiccolumn.

A lens forming composition was prepared by mixing 967.75 grams ofPRO-629 with 12.84 grams of the 2.5%2(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethyl)phenolultraviolet/visible light absorber stock solution, 4.3 grams of the 70%CN-384 co-initiator stock solution, 8.16 grams of the 2.5% CGI-819photoinitiator stock solution, 0.53 grams of the CN-386, 1.54 grams ofthe Tinuvin 400 ultraviolet/visible light absorber stock solution, 0.92grams of the Tinuvin 292 ultraviolet light stabilizer stock solution,and 4.0 grams of the background dye stock solution. The resulting lensforming composition contained the following components:

Material % by weight PRO-629 99.10% 2(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethyl)phenol 321 ppm Tinuvin 400 77 ppm Tinuvin 292 51 ppm CN-3840.3% CN-386 0.53% CGI-819 204 ppm Thermoplast Red 0.12 ppm Zapon Brown286 0.10 ppm Zapon Brown 287 0.10 ppm Oil Soluble Blue II 0.22 ppmThermoplast Blue 0.22 ppm

An 80 mm diameter flattop concave glass mold with a distance radius ofcurvature of 2.85 diopters and a +3.00 diopter bifocal add power wascleaned and coated as described in Example 10.

An 80 mm diameter convex mold with radii of curvature of 7.05 diopterswas cleaned and coated in the same fashion described above except thatno pooling of the coating composition occurred in the center of the moldwhen the composition was dispensed thereto.

Both the concave and convex molds were then provided with a curedadhesion-promoting coating composition. By providing such a coating, theadhesion between the casting surface of the glass mold and the lensforming composition was increased, thereby reducing the possibility ofpremature release of the lens from the mold. The coating furtherprovided abrasion resistance, chemical resistance, and improvedcosmetics to the finished lens.

The concave and convex molds were then assembled and placed within alens curing unit as described in Example 10.

An activating light filter was then placed on top of the back mold. Thefilter was approximately 80 mm in diameter which is the same as the molddiameter. It had a plano configuration with a thickness of 3.1 mm. Thisfilter transmitted approximately 30% of the incident activating lightfrom the source as measured using the IL1400 radiometer with a XRL-340Bdetector head. The filter was taken from a group of previously madefilters. The fabrication of these filters was discussed in Example 10.

The mold/gasket assembly in which the lens forming composition had beenplaced and which had been covered by the above described filter was thenirradiated with four consecutive doses of activating light totalingapproximately 600 mJ/cm², as measured using the IL-1400 Radiometerequipped with the XLR-340B detector. This measurement was taken at theplane of the mold cavity while no filter or any intervening media waspresent between the light source and the plane. The mold/gasket assemblywas then turned over on the stage so that the front mold was facingupward. The mold/gasket assembly was further rotated 90 degrees aroundthe paraxial axis from its original position. The light filter was thenreplaced over the front mold. The entire assembly was exposed to twomore doses of activating light totaling approximately 300 mJ/cm².

The mold/gasket assembly was then removed from the curing chamber, andthe gasket was removed from the assembly. The mold was then returned tothe lens curing chamber such that the back mold was facing upward. Anopaque rubber disc, approximately 80 mm in diameter was placed over theback mold. This disc had the function of preventing activating lightfrom impinging on the major portion of the material contained within thecavity. With the disc in position, the cell was exposed to two moreexposures at 300 mJ/ cm². This subsequent exposure was used to cure theresidual liquid around the edges of the lens, particularly around thejunction between the front mold and the lens and to help seal theperiphery. The mold assembly was removed from the curing chamber andplaced in a vertical orientation in a rack. The non-casting faces ofboth the front and back molds were then exposed to ambient roomtemperature air for a period of approximately fifteen minutes. At thispoint, the entire mold assembly was dosed with two exposures totaling300 mJ/cm² directed toward the back mold and two exposures totaling 300mJ/cm² directed toward the front mold, without the aforementioned lightfilter or opaque disc in place.

The lens was removed from the mold assembly and post-cured as describedin Example 10.

The resulting lens was approximately 72 mm in diameter, had a centerthickness of 1.5 mm, a distance focusing power of −4.08 diopters, and abifocal addition strength of 3.00 diopters. The resultant lens was waterwhite. The optics of the lens were crisp, without aberrations in eitherthe distance or the bifocal segment regions. The same lens formingcomposition was cured to form a piano lens. The piano lens was scannedwith a Hewlett Packard Model 8453 UV-Vis spectrophotometer. See FIG. 31for a plot of % transmittance versus wavelength (nm), as exhibited bythe photochromic lens when exposed to sunlight. The lens exhibitedvirtually no transmittance of light at wavelengths below about 370 nm.Also shown in FIG. 31 are the results of a similar scan made on a pianolens formed using the OMB-91 lens forming composition (see Curing by theApplication of Pulsed Activating Light above for components of OMB-91).The OMB-91 lens, which has no ultraviolet/visible light absorbingcompounds, appears to transmit light at wavelengths shorter than 370 nm,unlike the colorless lens that contained ultraviolet/visible lightabsorbing compounds.

The eyeglass lens of this example was cured using activating light eventhough the lens forming composition included activating light absorbingcompounds. Since activating light absorbing compounds tend to absorbactivating light strongly, the activating light might not havepenetrated to the depths of the lens forming composition. The lensforming composition, however, contained a co-initiator in conjunctionwith a photoinitiator to help promote the curing of the entire lensforming composition. The present example thus demonstrates that a lenscontaining ultraviolet/visible light absorbing compounds may be curedusing activating light to initiate polymerization of a lens formingcomposition which contains a photoinitiator/co-initiator system. Thelens was also produced using activating light of comparable intensityand duration as was used for the production of photochromic lenses.Thus, the addition of ultraviolet/visible light absorbers to anon-photochromic lens forming composition, allows both photochromic andnon-photochromic lens forming compositions to be cured using the sameapparatus and similar procedures.

Example 12 Casting a Colored Lens Containing Ultraviolet Visible LightAbsorbers

According to a preferred embodiment, a polymerizable mixture of PRO-629(see above for a description of the components of PRO-629), fixedpigments, and a photoinitiator/co-initiator package was preparedaccording to the following procedure. Nine separate stock solutions wereprepared. Seven of the stock solutions contained fixed pigments, one ofthe stock solutions contained an ultraviolet/visible light absorbingcompound, and one of the stock solutions contained a photoinitiator.Each of these stock solutions were treated by passing them through a oneinch diameter column packed with approximately 30 grams of aluminabasic. It is believed that this step reduces the impurities and trapsthe acidic byproducts present in each of the additives to the PRO-629.

For each of the following fixed pigments, a stock solution was preparedby the following procedure. The pigments used were Thermoplast Red 454,Thermoplast Blue P, Oil Soluble Blue II, Zapon Green 936, Zapon Brown286, Zapon Brown 287, and Thermoplast Yellow 284. One gram of eachpigment was dissolved in 499 grams of HDDMA. Each mixture was heated toa temperature in the range of from about 50° C. to about 60° C. forapproximately two hours. This mixture was passed through an aluminabasic column. The alumina was then washed with 200 grams of HDDMA at atemperature of about 50° C. to about 60° C. followed by 300 grams ofPRO-629 at a temperature of about 50° C. to about 60° C. This washingstep ensured that any pigments trapped in the alumina were washed intothe stock solution. This resulted in stock solutions which contained a0.1% concentration of each pigment in 29.97% PRO-629 and 69.93% HDDMA.

About 250 grams of the ultraviolet/visible light absorber stock solutionwas prepared by dissolving 5.0% Tinuvin 400 by weight in PRO-629. Thismixture was passed through an alumina basic column.

About 500 grams of the photoinitiator stock solution was prepared bydissolving 2.5% by weight of bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylphenyl) phosphine oxide (CGI-819 commercially availablefrom Ciba Additives) in PRO-629. This mixture was passed through analumina basic column in the dark.

A lens forming composition was prepared by mixing 685.3 grams of PRO-629with 10.48 grams of the 2.5% CGI-819 photoinitiator stock solution, 5.3grams of NMDEA (N-methyldiethanolamine is commercially available fromAldrich Chemicals), 0.6 grams of Tinuvin 400 ultraviolet/visible lightabsorber stock solution, 7 grams of the Thermoplast Red stock solution,58.3 grams of the Thermoplast Blue stock solution, 55.5 of the OilSoluble Blue II stock solution, 29.2 grams of the Zapon Green 936 stocksolution, 68.1 grams of the Zapon Brown 286 stock solution, 38.9 gramsof the Zapon Brown 287 stock solution, and 41.3 grams of the ThermoplastYellow 104 stock solution. The resulting lens forming compositioncontained the following components:

Material % by weight Bisphenol A bis allyl carbonate 13.35%Tripropyleneglycol diacrylate 25.13% Tetraethyleneglycol diacrylate16.49% Trimethylolpropane triacrylate 15.71% Hexanediol dimethacrylate28.75% Thermoplast Red 7.0 ppm Zapon Brown 286 68.1 ppm Zapon Brown 28738.9 ppm Oil Soluble Blue II 55.5 ppm Thermoplast Blue 58.3 ppm ZaponGreen 936 29.2 ppm Thermoplast Yellow 104 41.3 ppm NMDEA 0.53% CGI-819262 ppm Tinuvin 400 30 ppm

An 80 mm diameter flattop concave glass mold with a distance radius ofcurvature of 6.0 diopters was cleaned and coated as described in Example10.

An 80 mm diameter convex mold with radii of curvature of 6.05 diopterswas cleaned and coated in the same fashion except that no pooling of thecoating composition occurred in the center of the mold when thecomposition was dispensed thereto.

The concave and convex molds were then coated with a curedadhesion-promoting coating composition. By providing such a coating, theadhesion between the casting surface of the glass mold and the curinglens forming composition was increased, thereby reducing the possibilityof premature release of the lens from the mold. The coating alsoprovided abrasion resistance, chemical resistance, and improvedcosmetics to the finished lens.

The concave and convex molds were then assembled and placed within alens curing unit as described in Example 10.

An activating light filter was then placed on top of the back mold. Thefilter was approximately 80 mm in diameter, which is the same as themold diameter. It had a plano configuration with a thickness of 3.1 mm.This filter transmitted approximately 30% of the incident activatinglight from the source as measured using the IL 1400 radiometer with aXRL-340B detector head. The filter was taken from a group of previouslymade filters. The fabrication of these filters was discussed in Example10.

The mold/gasket assembly containing the lens forming composition wasthen irradiated with six consecutive doses of activating light totalingapproximately 1725 mJ/cm², as previously measured using the EL-1400Radiometer equipped with the XLR-340B detector, at the plane of the moldcavity with no filter or any intervening media between the light sourceand the plane. The mold/gasket assembly was then turned over on thestage so that the front mold was facing upward. The entire assembly wasthen exposed to six more doses of activating light totalingapproximately 1725 mJ/cm². The mold/gasket assembly was removed from thecuring chamber. The gasket was removed from the molds, and the assemblywas placed in a vertical orientation in a rack such that the non-castingfaces of both the front and back molds were exposed to ambient roomtemperature air for a period of approximately ten minutes. At thispoint, the assembly was returned to the lens curing chamber and wasdosed with four exposures totaling 600 mJ/cm² directed toward the backmold and four exposures totaling 600 mJ/cm² directed toward the frontmold.

The lens was removed from the mold assembly and post-cured as describedin Experiment 10.

The resulting lens was approximately 74 mm. in diameter, had a centerthickness of 2.7 mm, and a distance focusing power of +0.06 diopters.The resultant lens was dark green/grayish in color and could be used asa sunglass lens. The optics of the lens were crisp, without aberrations.The lens exhibited visible light transmission of approximately 10%. Whenscanned with a Hewlett Packard Model UV-Vis spectrophotometer, the lenstransmitted virtually no light at wavelengths less than 650 nm.

The sunglass lens of this example was cured using activating light eventhough the lens forming composition included ultraviolet/visibleabsorbing fixed pigments. Since such fixed pigments tend to absorb aportion of the activating light strongly, the activating light might nothave penetrated to the depths of the lens forming composition. The lensforming composition, however, contained a co-initiator in conjunctionwith a photoinitiator to help promote the curing of the entire lensforming composition. The present example thus demonstrates that asunglass lens containing ultraviolet/visible light absorbing fixedpigments may be cured using activating light, which includesultraviolet/visible light, to initiate polymerization of a lens formingcomposition that contains a photoinitiator/co-initiator system.

Example 13 Altering the Activated color of a Photochromic Lens

According to a preferred embodiment, a polymerizable mixture of PRO-629(see above for a description of the components of PRO-629), fixedpigments, a photoinitiator/co-initiator, and two photochromic compoundswas prepared in a manner similar to that described in Example 12. Theresulting lens forming composition includes PRO-629, and the followingcomponents:

Material amount IRG-184 80 ppm IRG 819 280 ppm CN-384 1.0% CN-386 1.0%Thermoplast Blue 0.67 ppm Thermoplast Red 0.04 ppm Reversacol Sea Green300 ppm Reversacol Berry Red 600 ppm

After the lens forming composition was prepared, a variety of lighteffectors were added to the lens forming composition described above.The modified lens forming composition was then placed within a moldcavity, prepared as described in Example 12.

Both sides of the mold assembly was irradiated with two doses of actiniclight (e.g., light having a wavelength above about 380 nm). The firstdose was applied for between 20 to 40 seconds. The final dose wasapplied for about 5 minutes. The resulting lens was demolded and treatedwith additional actinic light in a post-cure unit. The formed lens wasexposed to sunlight and the activated color of the lens observed. Thefollowing table summarizes the results when MEHQ, Tinuvin 400, ITX, andIRG-369 are used as light effectors. S9 represents a lens formed withoutany added light effectors.

EF- EFFECTOR UV ACTIVATED SAMPLE FECTOR AMOUNT ABSORBANCE COLOR S9 None— — Gray S10 MEHQ 350 ppm 294-317 nm Brown S11 Tinuvin 1130 ppm 295-390nm Aqua-Green 400 S12 ITX 500 ppm 280-415 nm Yellow-Green S13 IRG-369300 ppm 290-390 nm Green

The activated color of the formed lens was noted after exposing theformed lens to sunlight. The presence of light effectors can have asignificant effect on the color of the lens. It should be noted thatthis change in color may be obtained without altering the relative ratioof the photochromic compounds (i.e., Berry Red and Sea Green). MEHQwhich exhibits absorption in the low ultraviolet light region tends toshift the color of the lens toward red, thus causing the lens to take ona brown color when exposed to sunlight. The absorbers Tinuvin 400, ITX,and IRG-369 all tend to produce lenses having various green shades.Because of the broad photochromic activating light absorbance range ofthese compounds they may be effecting the photochromic activity of bothphotochromic compounds.

The above examples represent specific examples of how an activated colorof a lens may be altered by the addition of a light effector to a lensforming composition. By running similar studies with other lighteffectors, the activated color of a lens may be adjusted to a variety ofdifferent colors (e.g., red, orange, yellow, green, blue, indigo, orviolet) without changing the nature of the photochromic compounds.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

What is claimed is:
 1. A method for making a plastic eyeglass lens,comprising: placing a liquid lens forming composition in a mold cavitydefined by at least a first mold member and a second mold member, thelens forming composition comprising: a monomer composition comprising anaromatic containing polyethylenic polyether functional monomer havingthe general structure:R²—[CH₂—(CH₂)_(m)—O]_(j)—A₁—[O—(CH₂)_(n)—CH₂]_(k)—R²  where m and n areeach independently 1 or 2; where j and k are each independently between1 and 20; R² is vinyl, allyl, methacrylyl, acrylyl, methacrylate, oracrylate; and A₁ is a dihydroxy aromatic-containing material; aphotoinitiator configured to initiate polymerization of the monomercomposition in response to being exposed to activating light during use;and directing activating light toward at least one of the mold membersto cure the lens forming composition to form the eyeglass lens.
 2. Themethod of claim 1 wherein curing the lens forming composition comprisespolymerizing the monomer composition.
 3. The method of claim 1 whereindirecting activating light to the lens forming composition comprisesapplying a plurality of activating light pulses to the lens formingcomposition.
 4. The method of claim 1, further comprising applying ahydrophobic coating to the eyeglass lens.
 5. The method of claim 1,further comprising applying a hydrophobic coating to the eyeglass lens,wherein the hydrophobic coating is adapted to inhibit the eyeglass lensfrom being exposed to water and to ambient oxygen.
 6. The method ofclaim 1 wherein the first mold member comprises a casting face and anon-casting face, and further comprising placing a first hardcoat layerupon said casting face and a second hardcoat layer upon said firsthardcoat layer prior to placing the liquid lens forming composition inthe mold cavity.
 7. The method of claim 1 wherein the second mold membercomprises a casting face and a non-casting face, and further comprisingplacing a material capable of being tinted upon the casting face priorto placing the liquid lens forming composition in the mold cavity. 8.The method of claim 1 wherein the second mold member comprises a castingface and a non-casting face, and further comprising placing a materialcapable of being tinted upon the casting face prior to placing theliquid lens forming composition in the mold cavity, and furthercomprising applying dye to the material to tint the lens formingcomposition.
 9. The method of claim 1, further comprising applying anadhesion-promoter coating to an inner surface of the first mold memberand an inner surface of the second mold member to substantially adherethe lens forming composition to the first and second mold members. 10.The method of claim 1 wherein the activating light is removed from themold members when substantially all of the lens forming composition hasreached its gel point.
 11. The method of claim 1 wherein the activatinglight comprises a first intensity, and herein the activating light isdirected toward at least one of the mold members until substantially allof the lens forming composition has reached its gel point, and furthercomprising directing activating light having a second intensity towardsat least one mold member to cure substantially all of the lens formingcomposition, the first intensity being greater than the secondintensity.
 12. The method of claim 1 wherein the activating light isdirected toward at least one of the mold members until substantially allof the lens forming composition has reached its gel point, and furthercomprising inhibiting the activating light from further being directedtoward the mold members, thereby allowing substantially all of the lensforming composition to cure.
 13. The method of claim 1 wherein theeyeglass lens is formed from the lens forming composition in a timeperiod of less than about 10 minutes.
 14. The method of claim 1 whereinthe eyeglass lens is formed from the lens forming composition in a timeperiod of less than about 30 minutes.
 15. The method of claim 1 whereinthe first mold member is spaced apart from the second mold member by agasket, and further comprising removing the gasket subsequent todirecting activating light to at least one of the mold members to exposethe lens forming composition to ambient air for approximately 5 to 30minutes, thereby cooling the lens forming composition, and furthercomprising directing additional activating light toward at least one ofthe mold members to at least partially cure the lens formingcomposition.
 16. The method of claim 1, further comprising heating thecured lens forming composition to a temperature between approximately100° C. to 120° C. for approximately 3 to 15 minutes subsequent tocuring the lens forming composition.
 17. The method of claim 1, furthercomprising placing a filter substantially adjacent to at least one ofthe mold members, wherein the filter comprises a varying thickness suchthat the filter varies an intensity distribution of activating lightacross the mold members.
 18. The method of claim 1 wherein an amount ofactivating light is directed towards the mold cavity, and wherein themold cavity comprises a temperature, and wherein the amount ofactivating light directed to the mold cavity is a function of thetemperature of at least a portion of the mold cavity.
 19. The method ofclaim 1 wherein directing light to the lens forming compositioncomprises applying a number of activating light pulses to the lensforming composition, wherein the number of light pulses is a function ofa change in a temperature of the lens forming composition over a periodof time.
 20. The method of claim 1 wherein directing light to the lensforming composition comprises applying a plurality of activating lightpulses to the lens forming composition, wherein a duration of the lightpulses is a function of a change in a temperature of the lens formingcomposition over a period of time.
 21. The method of claim 1 whereindirecting light to the lens forming composition comprises applying aplurality of activating light pulses to the lens forming composition,wherein an intensity of the light pulses is a function of a change in atemperature of the lens forming composition over a predetermined periodof time.